fixed version for site badge

+added console support to lyng/jlyng CLI
+added unicode escapes
+created tetris console sample

.gitattributes

@@ -0,0 +1 @@
+*.zip filter=lfs diff=lfs merge=lfs -text

.gitignore

@@ -16,3 +16,14 @@ xcuserdata
 /test.lyng
 /sample_texts/1.txt.gz
 /kotlin-js-store/wasm/yarn.lock
+/distributables
+.output*.txt
+debug.log
+/build.log
+/test.md
+/build_output.txt
+/build_output_full.txt
+/check_output.txt
+/compile_jvm_output.txt
+/compile_metadata_output.txt
+test_output*.txt

.junie/guidelines.md

@@ -0,0 +1,11 @@
+# Lyng Project Guidelines
+
+This project uses the Lyng scripting language for multiplatform scripting.
+
+## Coding in Lyng
+When writing, refactoring, or analyzing Lyng code:
+- **Reference**: Always use `LYNG_AI_SPEC.md` in the project root as the primary source of truth for syntax and idioms.
+- **File Extensions**: Use `.lyng` for all script files.
+- **Implicit Coroutines**: Remember that all Lyng functions are implicitly coroutines; do not look for `async/await`.
+- **Everything is an Expression**: Leverage the fact that blocks, if-statements, and loops return values.
+- **Maps vs Blocks**: Be careful: `{}` is a block/lambda, use `Map()` for an empty map.

.run/Tests in 'lyng.lynglib.jvmTest'.run.xml

@@ -0,0 +1,28 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="Tests in 'lyng.lynglib.jvmTest'" type="GradleRunConfiguration" factoryName="Gradle">
+    <ExternalSystemSettings>
+      <option name="executionName" />
+      <option name="externalProjectPath" value="$PROJECT_DIR$" />
+      <option name="externalSystemIdString" value="GRADLE" />
+      <option name="scriptParameters" value="" />
+      <option name="taskDescriptions">
+        <list />
+      </option>
+      <option name="taskNames">
+        <list>
+          <option value=":lynglib:cleanJvmTest" />
+          <option value=":lynglib:jvmTest" />
+        </list>
+      </option>
+      <option name="vmOptions" />
+    </ExternalSystemSettings>
+    <ExternalSystemDebugServerProcess>false</ExternalSystemDebugServerProcess>
+    <ExternalSystemReattachDebugProcess>true</ExternalSystemReattachDebugProcess>
+    <ExternalSystemDebugDisabled>false</ExternalSystemDebugDisabled>
+    <DebugAllEnabled>false</DebugAllEnabled>
+    <RunAsTest>true</RunAsTest>
+    <GradleProfilingDisabled>false</GradleProfilingDisabled>
+    <GradleCoverageDisabled>false</GradleCoverageDisabled>
+    <method v="2" />
+  </configuration>
+</component>

.run/lyng_site [jsBrowserDevelopmentRun].run.xml

@@ -0,0 +1,44 @@
+<!--
+  ~ Copyright 2025 Sergey S. Chernov real.sergeych@gmail.com
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~     http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  ~
+  -->
+
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="lyng:site [jsBrowserDevelopmentRun]" type="GradleRunConfiguration" factoryName="Gradle">
+    <ExternalSystemSettings>
+      <option name="executionName" />
+      <option name="externalProjectPath" value="$PROJECT_DIR$/site" />
+      <option name="externalSystemIdString" value="GRADLE" />
+      <option name="scriptParameters" value="--continuous" />
+      <option name="taskDescriptions">
+        <list />
+      </option>
+      <option name="taskNames">
+        <list>
+          <option value="jsBrowserDevelopmentRun" />
+        </list>
+      </option>
+      <option name="vmOptions" />
+    </ExternalSystemSettings>
+    <ExternalSystemDebugServerProcess>true</ExternalSystemDebugServerProcess>
+    <ExternalSystemReattachDebugProcess>true</ExternalSystemReattachDebugProcess>
+    <ExternalSystemDebugDisabled>false</ExternalSystemDebugDisabled>
+    <DebugAllEnabled>false</DebugAllEnabled>
+    <RunAsTest>false</RunAsTest>
+    <GradleProfilingDisabled>true</GradleProfilingDisabled>
+    <GradleCoverageDisabled>true</GradleCoverageDisabled>
+    <method v="2" />
+  </configuration>
+</component>

AGENTS.md

@@ -0,0 +1,33 @@
+# AI Agent Notes
+
+## Canonical AI References
+- Use `docs/ai_language_reference.md` as the primary, compiler-verified Lyng language reference for code generation.
+- For generics-heavy code generation, follow `docs/ai_language_reference.md` section `7.1 Generics Runtime Model and Bounds` and `7.2 Differences vs Java / Kotlin / Scala`.
+- Use `docs/ai_stdlib_reference.md` for default runtime/module APIs and stdlib surface.
+- Treat `LYNG_AI_SPEC.md` and older docs as secondary if they conflict with the two files above.
+
+## Kotlin/Wasm generation guardrails
+- Avoid creating suspend lambdas for compiler runtime statements. Prefer explicit `object : Statement()` with `override suspend fun execute(...)`.
+- Do not use `statement { ... }` or other inline suspend lambdas in compiler hot paths (e.g., parsing/var declarations, initializer thunks).
+- If you need a wrapper for delegated properties, check for `getValue` explicitly and return a concrete `Statement` object when missing; avoid `onNotFoundResult` lambdas.
+- If wasmJs browser tests hang, first run `:lynglib:wasmJsNodeTest` and look for wasm compilation errors; hangs usually mean module instantiation failed.
+- Do not increase test timeouts to mask wasm generation errors; fix the invalid IR instead.
+
+## Type inference notes (notes/new_lyng_type_system_spec.md)
+- Nullability is Kotlin-style: `T` non-null, `T?` nullable, `!!` asserts non-null.
+- `void` is a singleton of class `Void` (syntax sugar for return type).
+- Object members are always allowed even on unknown types; non-Object members require explicit casts. Remove `inspect` from Object and use `toInspectString()` instead.
+- Type expression checks: `x is T` is value instance check; `T1 is T2` is type-subset; `A in T` means `A` is subset of `T`; `==` is structural type equality.
+- Type aliases: `type Name = TypeExpr` (generic allowed) expand to their underlying type expressions; no nominal distinctness.
+- Bounds and variance: `T: A & B` / `T: A | B` for bounds; declaration-site variance with `out` / `in`.
+- Do not reintroduce bytecode fallback opcodes (e.g., `GET_NAME`, `EVAL_*`, `CALL_FALLBACK`) or runtime name-resolution fallbacks; all symbol resolution must stay compile-time only.
+
+## Bytecode frame-first migration plan
+- Treat frame slots as the only storage for locals/temps by default; avoid pre-creating scope slot mappings for compiled functions.
+- Create closure references only when a capture is detected; use a direct frame+slot reference (foreign slot ref) instead of scope slots.
+- Keep Scope as a lazy reflection facade: resolve name -> slot only on demand for Kotlin interop (no eager name mapping on every call).
+- Avoid PUSH_SCOPE/POP_SCOPE in bytecode for loops/functions unless dynamic name access or Kotlin reflection is requested.
+
+## ABI proposal notes
+- Runtime generic metadata for generic extern classes is tracked in `proposals/extern_generic_runtime_abi.md`.
+- Keep this design `Obj`-centric: do not assume extern-class values are `ObjInstance`; collection must be enabled on `ObjClass`.

CHANGELOG.md

@@ -1,6 +1,117 @@
-## Changelog
+## 1.5.0-SNAPSHOT
 
-### Unreleased
+### Language Features
+- Added `return` statement with local and non-local exit support (`return@label`).
+- Support for `abstract` classes, methods, and variables.
+- Introduced `interface` as a synonym for `abstract class`.
+- Multiple Inheritance (MI) completed and enabled by default (C3 MRO).
+- Class properties with custom accessors (`get`, `set`).
+- Restricted setter visibility (`private set`, `protected set`).
+- Late-initialized `val` fields in classes with `Unset` protection.
+- Named arguments (`name: value`) and named splats (`...Map`).
+- Assign-if-null operator `?=`.
+- Refined `protected` visibility rules and `closed` modifier.
+- Transient attribute `@Transient` for serialization and equality.
+- Unified Delegation model for `val`, `var`, and `fun`.
+- Singleton objects (`object`) and object expressions.
+
+### Standard Library
+- Added `with(self, block)` for scoped execution.
+- Added `clamp()` function and extension.
+- Improved `Exception` and `StackTraceEntry` reporting.
+
+### Tooling and IDE
+- **CLI**: Added `fmt` as a first-class subcommand for code formatting.
+- **IDEA Plugin**: Lightweight autocompletion (experimental), improved docs, and Grazie integration.
+- **Highlighters**: Updated TextMate bundle and website highlighters for new syntax.
+
+### Detailed Changes:
+
+- Language: Refined `protected` visibility rules
+  - Ancestor classes can now access `protected` members of their descendants, provided the ancestor also defines or inherits a member with the same name (indicating an override of a member known to the ancestor).
+  - This allows patterns where a base class calls a `protected` method that is implemented in a subclass.
+  - Fixed a regression where self-calls to unmangled members sometimes bypassed visibility checks incorrectly; these are now handled by the refined logic.
+
+- Language: Added `return` statement
+  - `return [expression]` exits the innermost enclosing callable (function or lambda).
+  - Supports non-local returns using `@label` syntax (e.g., `return@outer 42`).
+  - Named functions automatically provide their name as a label for non-local returns.
+  - Labeled lambdas: lambdas can be explicitly labeled using `@label { ... }`.
+  - Restriction: `return` is forbidden in shorthand function definitions (e.g., `fun f(x) = return x` is a syntax error).
+  - Control Flow: `return` and `break` are now protected from being caught by user-defined `try-catch` blocks in Lyng.
+  - Documentation: New `docs/return_statement.md` and updated `tutorial.md`.
+
+- Language: stdlib improvements
+  - Added `with(self, block)` function to `root.lyng` which executes a block with `this` set to the provided object.
+- Language: Abstract Classes and Interfaces
+  - Support for `abstract` modifier on classes, methods, and variables.
+  - Introduced `interface` as a synonym for `abstract class`, supporting full state (constructors, fields, `init` blocks) and implementation by parts via MI.
+  - New `closed` modifier (antonym to `open`) to prevent overriding class members.
+  - Refined `override` logic: mandatory keyword when re-declaring members that exist in the ancestor chain (MRO).
+  - MI Satisfaction: Abstract requirements are automatically satisfied by matching concrete members found later in the C3 MRO chain without requiring explicit proxy methods.
+  - Integration: Updated highlighters (lynglib, lyngweb, IDEA plugin), IDEA completion, and Grazie grammar checking.
+  - Documentation: Updated `docs/OOP.md` with sections on "Abstract Classes and Members", "Interfaces", and "Overriding and Virtual Dispatch".
+- IDEA plugin: Improved natural language support and spellchecking
+  - Disabled the limited built-in English and Technical dictionaries.
+  - Enforced usage of the platform's standard Natural Languages (Grazie) and Spellchecker components.
+  - Integrated `SpellCheckerManager` for word suggestions and validation, respecting users' personal and project dictionaries.
+  - Added project-specific "learned words" support via `Lyng Formatter` settings and quick-fixes.
+  - Enhanced fallback spellchecker for technical terms and Lyng-specific vocabulary.
+
+- Language: Class properties with accessors
+  - Support for `val` (read-only) and `var` (read-write) properties in classes.
+  - Syntax: `val name [ : Type ] get() { body }` or `var name [ : Type ] get() { body } set(value) { body }`.
+  - Laconic Expression Shorthand: `val prop get() = expression` and `var prop get() = read set(v) = write`.
+  - Properties are pure accessors and do **not** have automatic backing fields.
+  - Validation: `var` properties must have both accessors; `val` must have only a getter.
+  - Integration: Updated TextMate grammar and IntelliJ plugin (highlighting + keywords).
+  - Documentation: New "Properties" section in `docs/OOP.md`.
+
+- Language: Restricted Setter Visibility
+  - Support for `private set` and `protected set` modifiers on `var` fields and properties.
+  - Allows members to be publicly readable but only writable from within the declaring class or its subclasses.
+  - Enforcement at runtime: throws `AccessException` on unauthorized writes.
+  - Supported only for declarations in class bodies (fields and properties).
+  - Documentation: New "Restricted Setter Visibility" section in `docs/OOP.md`.
+
+- Language: Late-initialized `val` fields in classes
+  - Support for declaring `val` without an immediate initializer in class bodies.
+  - Compulsory initialization: every late-init `val` must be assigned at least once within the class body or an `init` block.
+  - Write-once enforcement: assigning to a `val` is allowed only if its current value is `Unset`.
+  - Access protection: reading a late-init `val` before it is assigned returns the `Unset` singleton; using `Unset` for most operations throws an `UnsetException`.
+  - Extension properties do not support late-init.
+  - Documentation: New "Late-initialized `val` fields" and "The `Unset` singleton" sections in `docs/OOP.md`.
+
+- Docs: OOP improvements
+  - New page: `docs/scopes_and_closures.md` detailing `ClosureScope` resolution order, recursion‑safe helpers (`chainLookupIgnoreClosure`, `chainLookupWithMembers`, `baseGetIgnoreClosure`), cycle prevention, and capturing lexical environments for callbacks (`snapshotForClosure`).
+  - Updated: `docs/advanced_topics.md` (link to the new page), `docs/parallelism.md` (closures in `launch`/`flow`), `docs/OOP.md` (visibility from closures with preserved `currentClassCtx`), `docs/exceptions_handling.md` (compatibility alias `SymbolNotFound`).
+  - Tutorial: added quick link to Scopes and Closures.
+
+- IDEA plugin: Lightweight autocompletion (experimental)
+  - Global completion: local declarations, in‑scope parameters, imported modules, and stdlib symbols.
+  - Member completion: after a dot, suggests only members of the inferred receiver type (incl. chained calls like `Path(".." ).lines().` → `Iterator` methods). No global identifiers appear after a dot.
+  - Inheritance-aware: direct class members first, then inherited (e.g., `List` includes `Collection`/`Iterable` methods).
+  - Heuristics: handles literals (`"…"` → `String`, numbers → `Int/Real`, `[...]` → `List`, `{...}` → `Dict`) and static `Namespace.` members.
+  - Performance: capped results, early prefix filtering, per‑document MiniAst cache, cancellation checks.
+  - Toggle: Settings | Lyng Formatter → "Enable Lyng autocompletion (experimental)" (default ON).
+  - Stabilization: DEBUG completion/Quick Doc logs are OFF by default; behavior aligned between IDE and isolated engine tests.
+
+- Language: Named arguments and named splats
+  - New call-site syntax for named arguments using colon: `name: value`.
+    - Positional arguments must come before named; positionals after a named argument inside parentheses are rejected.
+    - Trailing-lambda interaction: if the last parameter is already assigned by name (or via a named splat), a trailing `{ ... }` block is illegal.
+  - Named splats: `...` can now expand a Map into named arguments.
+    - Only string keys are allowed; non-string keys raise a clear error.
+    - Duplicate assignment across named args and named splats is an error.
+    - Ellipsis (variadic) parameters remain positional-only and cannot be named.
+  - Rationale: `=` is assignment and an expression in Lyng; `:` at call sites avoids ambiguity. Declarations keep `name: Type`; call-site casts continue to use `as` / `as?`.
+  - Documentation updated: proposals and declaring-arguments sections now cover named args/splats and error cases.
+  - Tests added covering success cases and errors for named args/splats and trailing-lambda interactions.
+
+- Tooling: Highlighters and TextMate bundle updated for named args
+  - Website/editor highlighter (lyngweb + site) works with `name: value` and `...Map("k" => v)`; added JS tests covering punctuation/operator spans for `:` and `...`.
+  - TextMate grammar updated to recognize named call arguments: `name: value` after `(` or `,` with `name` highlighted as `variable.parameter.named.lyng` and `:` as punctuation; excludes `::`.
+  - TextMate bundle version bumped to 0.0.3; README updated with details and guidance.
 
 - Multiple Inheritance (MI) completed and enabled by default:
   - Active C3 Method Resolution Order (MRO) for deterministic, monotonic lookup across complex hierarchies and diamonds.
@@ -15,7 +126,7 @@
     - Header-specified constructor arguments are passed to direct bases.
   - Visibility enforcement under MI:
     - `private` visible only inside the declaring class body.
-    - `protected` visible inside the declaring class and any of its transitive subclasses; unrelated contexts cannot access it (qualification/casts do not bypass).
+    - `protected` visible inside the declaring class and its transitive subclasses. Additionally, ancestor classes can access protected members of their descendants if it's an override of a member known to the ancestor. Unrelated contexts cannot access it (qualification/casts do not bypass).
   - Diagnostics improvements:
     - Missing member/field messages include receiver class and linearization order; hints for `this@Type` or casts when helpful.
     - Invalid `this@Type` reports that the qualifier is not an ancestor and shows the receiver lineage.
@@ -23,6 +134,23 @@
 
 - Documentation updated (docs/OOP.md and tutorial quick-start) to reflect MI with active C3 MRO.
 
-Notes:
-- Existing single-inheritance code continues to work; resolution reduces to the single base.
-- If code previously relied on non-deterministic parent set iteration, C3 MRO provides a predictable order; disambiguate explicitly if needed using `this@Type`/casts.
+- CLI: Added `fmt` as a first-class Clikt subcommand.
+  - Default behavior: formats files to stdout (no in-place edits by default).
+  - Options:
+    - `--check`: check only; print files that would change; exit with code 2 if any changes are needed.
+    - `-i, --in-place`: write formatted result back to files.
+    - `--spacing`: apply spacing normalization.
+    - `--wrap`, `--wrapping`: enable line wrapping.
+  - Mutually exclusive: `--check` and `--in-place` together now produce an error and exit with code 1.
+  - Multi-file stdout prints headers `--- <path> ---` per file.
+  - `lyng --help` shows `fmt`; `lyng fmt --help` displays dedicated help.
+  - Fix: Property accessors (`get`, `set`, `private set`, `protected set`) are now correctly indented relative to the property declaration.
+  - Fix: Indentation now correctly carries over into blocks that start on extra‑indented lines (e.g., nested `if` statements or property accessor bodies).
+  - Fix: Formatting Markdown files no longer deletes content in `.lyng` code fences and works correctly with injected files (resolves clobbering, `StringIndexOutOfBoundsException`, and `nonempty text is not covered by block` errors).
+
+- CLI: Preserved legacy script invocation fast-paths:
+  - `lyng script.lyng [args...]` executes the script directly.
+  - `lyng -- -file.lyng [args...]` executes a script whose name begins with `-`.
+
+- CLI: Fixed a regression where the root help banner could print before subcommands.
+  - Root command no longer prints help when a subcommand (e.g., `fmt`) is invoked.

LYNG_AI_SPEC.md

@@ -0,0 +1,130 @@
+# Lyng Language AI Specification (V1.5.0-SNAPSHOT)
+
+High-density specification for LLMs. Reference this for all Lyng code generation.
+
+## 1. Core Philosophy & Syntax
+- **Everything is an Expression**: Blocks, `if`, `when`, `for`, `while`, `do-while` return their last expression (or `void`).
+- **Static Types + Inference**: Every declaration has a compile-time type (explicit or inferred). Types are Kotlin‑style: non‑null by default, nullable with `?`.
+- **Loops with `else`**: `for`, `while`, and `do-while` support an optional `else` block.
+    - `else` executes **only if** the loop finishes normally (without a `break`).
+    - `break <value>` exits the loop and sets its return value.
+    - Loop Return Value:
+        1. Value from `break <value>`.
+        2. Result of `else` block (if loop finished normally and `else` exists).
+        3. Result of the last iteration (if loop finished normally and no `else`).
+        4. `void` (if loop body never executed and no `else`).
+- **Implicit Coroutines**: All functions are coroutines. No `async/await`. Use `launch { ... }` (returns `Deferred`) or `flow { ... }`.
+- **Functions**: Use `fun` or the short form `fn`. Function declarations are expressions returning a callable.
+- **Variables**: `val` (read-only), `var` (mutable). Supports late-init `val` in classes (must be assigned in `init` or body).
+- **Serialization**: Use `@Transient` attribute before `val`/`var` or constructor parameters to exclude them from Lynon/JSON serialization. Transient fields are also ignored during `==` structural equality checks.
+- **Null Safety**: `?` (nullable type), `?.` (safe access), `?( )` (safe invoke), `?{ }` (safe block invoke), `?[ ]` (safe index), `?:` or `??` (elvis), `?=` (assign-if-null).
+- **Equality**: `==` (equals), `!=` (not equals), `===` (ref identity), `!==` (ref not identity).
+- **Comparison**: `<`, `>`, `<=`, `>=`, `<=>` (shuttle/spaceship, returns -1, 0, 1).
+- **Destructuring**: `val [a, b, rest...] = list`. Supports nested `[a, [b, c]]` and splats.
+- **Compile-Time Resolution Only**: All names/members must resolve at compile time. No runtime name lookup or fallback opcodes.
+
+## 2. Object-Oriented Programming (OOP)
+- **Multiple Inheritance**: Supported with **C3 MRO** (Python-style). Diamond-safe.
+- **Header Arguments**: `class Foo(a, b) : Base(a)` defines fields `a`, `b` and passes `a` to `Base`.
+- **Members**: `fun name(args) { ... }`, `val`, `var`, `static val`, `static fun`.
+- **Properties (Get/Set)**: Pure accessors, no auto-backing fields.
+    ```lyng
+    var age
+        get() = _age
+        private set(v) { if(v >= 0) _age = v }
+    // Laconic syntax:
+    val area get = π * r * r
+    ```
+- **Mandatory `override`**: Required for all members existing in the ancestor chain.
+- **Visibility**: `public` (default), `protected` (subclasses and ancestors for overrides), `private` (this class instance only). `private set` / `protected set` allowed on properties.
+- **Disambiguation**: `this@Base.member()` or `(obj as Base).member()`. `as` returns a qualified view.
+- **Abstract/Interface**: `interface` is a synonym for `abstract class`. Both support state and constructors.
+- **Extensions**: `fun Class.ext()` or `val Class.ext get = ...`. Scope-isolated.
+- **Member Access**: Object members (`toString`, `toInspectString`, `let`, `also`, `apply`, `run`) are allowed on unknown types; all other members require a statically known receiver type or explicit cast.
+
+## 2.1 Type System (2026)
+- **Root Type**: Everything is an `Object` (root of the hierarchy).
+- **Nullability**: Non-null by default (`T`), nullable with `T?`, `!!` asserts non-null.
+- **Untyped params**: `fun foo(x)` -> `x: Object`, `fun foo(x?)` -> `x: Object?`.
+- **Untyped vars**: `var x` is `Unset` until first assignment locks the type (including nullability).
+  - `val x = null` -> type `Null`; `var x = null` -> type `Object?`.
+- **Inference**:
+  - List literals infer union element types; empty list defaults to `List<Object>` unless constrained.
+  - Map literals infer key/value types; empty map defaults to `Map<Object, Object>` unless constrained.
+  - Mixed numeric ops promote `Int` + `Real` to `Real`.
+- **Type aliases**: `type Name = TypeExpr` (generic allowed). Aliases expand to their underlying type expressions (no nominal distinctness).
+- **Generics**: Bounds with `T: A & B` or `T: A | B`; variance uses `out`/`in` (declaration‑site only).
+- **Casts**: `as` is a runtime-checked cast; `as?` is safe-cast returning `null`. If the value is nullable, `as T` implies `!!`.
+
+## 2.2 Type Expressions and Checks
+- **Value checks**: `x is T` (runtime instance check).
+- **Type checks**: `T1 is T2` and `A in T` are subset checks between type expressions (compile-time where possible).
+- **Type equality**: `T1 == T2` is structural (unions/intersections are order‑insensitive).
+- **Compile-time enforcement**: Bounds are checked at call sites; runtime checks only appear when the compile‑time type is too general.
+
+## 3. Delegation (`by`)
+Unified model for `val`, `var`, and `fun`.
+```lyng
+val x by MyDelegate()
+var y by Map() // Uses "y" as key in map
+fn f(a, b) by RemoteProxy() // Calls Proxy.invoke(thisRef, "f", a, b)
+```
+Delegate Methods:
+- `getValue(thisRef, name)`: for `val`/`var`.
+- `setValue(thisRef, name, val)`: for `var`.
+- `invoke(thisRef, name, args...)`: for `fn` (called if `getValue` is absent).
+- `bind(name, access, thisRef)`: optional hook called at declaration/binding time. `access` is `DelegateAccess.Val`, `Var`, or `Callable`.
+
+## 4. Standard Library & Functional Built-ins
+- **Scope Functions**:
+    - `obj.let { it... }`: result of block. `it` is `obj`.
+    - `obj.apply { this... }`: returns `obj`. `this` is `obj`.
+    - `obj.also { it... }`: returns `obj`. `it` is `obj`.
+    - `obj.run { this... }`: result of block. `this` is `obj`.
+    - `with(obj, { ... })`: result of block. `this` is `obj`.
+- **Functional**: `forEach`, `map`, `filter`, `any`, `all`, `sum`, `count`, `sortedBy`, `flatten`, `flatMap`, `associateBy`.
+- **Lazy**: `val x = cached { expensive() }` (call as `x()`) or `val x by lazy { ... }`.
+- **Collections**: `List` ( `[a, b]` ), `Map` ( `Map(k => v)` ), `Set` ( `Set(a, b)` ). `MapEntry` ( `k => v` ).
+
+## 5. Patterns & Shorthands
+- **Map Literals**: `{ key: value, identifier: }` (identifier shorthand `x:` is `x: x`). Empty map is `{:}`.
+- **Named Arguments**: `fun(y: 10, x: 5)`. Shorthand: `Point(x:, y:)`.
+- **Varargs & Splats**: `fun f(args...)`, `f(...otherList)`.
+- **Labels**: `loop@ for(x in list) { if(x == 0) break@loop }`.
+- **Dynamic**: `val d = dynamic { get { name -> ... } }` allows `d.anyName` via explicit dynamic handler (not implicit fallback).
+
+## 6. Operators & Methods to Overload
+| Op | Method | Op | Method |
+| :--- | :--- | :--- | :--- |
+| `+` | `plus` | `==` | `equals` |
+| `-` | `minus` | `<=>` | `compareTo` |
+| `*` | `mul` | `[]` | `getAt` / `putAt` |
+| `/` | `div` | `!` | `logicalNot` |
+| `%` | `mod` | `-` | `negate` (unary) |
+| `=~` | `operatorMatch` | `+=` | `plusAssign` |
+
+## 7. Common Snippets
+```lyng
+// Multiple Inheritance and Properties
+class Warrior(id, hp) : Character(id), HealthPool(hp) {
+    override fun toString() = "Warrior #%s (%s HP)"(id, hp)
+}
+
+// Map entry and merging
+val m = Map("a" => 1) + ("b" => 2)
+m += "c" => 3
+
+// Destructuring with splat
+val [first, middle..., last] = [1, 2, 3, 4, 5]
+
+// Safe Navigation and Elvis
+val companyName = person?.job?.company?.name ?: "Freelancer"
+```
+
+## 8. Standard Library Discovery
+To collect data on the standard library and available APIs, AI should inspect:
+- **Global Symbols**: `lynglib/src/commonMain/kotlin/net/sergeych/lyng/Script.kt` (root functions like `println`, `sqrt`, `assert`).
+- **Core Type Members**: `lynglib/src/commonMain/kotlin/net/sergeych/lyng/obj/*.kt` (e.g., `ObjList.kt`, `ObjString.kt`, `ObjMap.kt`) for methods on built-in types.
+- **Lyng-side Extensions**: `lynglib/stdlib/lyng/root.lyng` for high-level functional APIs (e.g., `map`, `filter`, `any`, `lazy`).
+- **I/O & Processes**: `lyngio/src/commonMain/kotlin/net/sergeych/lyng/io/` for `fs` and `process` modules.
+- **Documentation**: `docs/*.md` (e.g., `tutorial.md`, `lyngio.md`) for high-level usage and module overviews.

README.md

@@ -1,45 +1,62 @@
-# Lyng: modern scripting for kotlin multiplatform
+# Lyng: ideal scripting for kotlin multiplatform
+
+__Please visit the project homepage: [https://lynglang.com](https://lynglang.com) and a [telegram channel](https://t.me/lynglang).__
+
+__Main development site:__ [https://gitea.sergeych.net/SergeychWorks/lyng](https://gitea.sergeych.net/SergeychWorks/lyng)
+__github mirror__: [https://github.com/sergeych/lyng](https://github.com/sergeych/lyng)
+
+We keep github as a mirror and backup for the project, while the main development site is hosted on gitea.sergeych.net. We use gitea for issues and pull requests, and as a main point of trust, as github access now is a thing that can momentarily be revoked for no apparent reason.
+
+We encourage using the github if the main site is not accessible from your country and vice versa. We recommend to `publishToMavenLocal` and not depend on politics.
 
-A KMP library and a standalone interpreter
 
 - simple, compact, intuitive and elegant modern code:
 
-```
-class Point(x,y) {
+```lyng
+class Point(x, y) {
    fun dist() { sqrt(x*x + y*y) } 
 }
-Point(3,4).dist() //< 5
+
+// Auto-named arguments shorthand (x: is x: x):
+val x = 3
+val y = 4
+Point(x:, y:).dist() //< 5
 
 fun swapEnds(first, args..., last, f) {
     f( last, ...args, first)
 } 
+
+class A {
+    class B(x?)
+    object Inner { val foo = "bar" }
+    enum E* { One, Two }
+}
+val ab = A.B()
+assertEquals(null, ab.x)
+assertEquals("bar", A.Inner.foo)
+assertEquals(A.E.One, A.One)
 ```
 
 - extremely simple Kotlin integration on any platform (JVM, JS, WasmJS, Lunux, MacOS, iOS, Windows)
 - 100% secure: no access to any API you didn't explicitly provide
-- 100% coroutines! Every function/script is a coroutine, it does not block the thread, no async/await/suspend keyword garbage, see [parallelism]
-
-```
-  val deferred = launch {
-    delay(1.5) // coroutine is delayed for 1.5s, thread is not blocked!
-    "done"
-  }
-  // ...
-  // suspend current coroutine, no thread is blocked again,
-  // and wait for deferred to return something:
-  assertEquals("donw", deferred.await())
-```
-and it is multithreaded on platforms supporting it (automatically, no code changes required, just
-`launch` more coroutines and they will be executed concurrently if possible). See [parallelism]
-
-- functional style and OOP together, multiple inheritance, implementing interfaces for existing classes, writing extensions.
+- 100% coroutines! Every function/script is a coroutine, it does not block the thread, no async/await/suspend keyword garbage, see [parallelism]. it is multithreaded on platforms supporting it (automatically, no code changes required, just `launch` more coroutines and they will be executed concurrently if possible). See [parallelism]
+- functional style and OOP together: multiple inheritance (so you got it all - mixins, interfaces, etc.), delegation, sigletons, anonymous classes,extensions.
+- nice literals for maps and arrays, destructuring assignment, ranges.
 - Any Unicode letters can be used as identifiers: `assert( sin(π/2) == 1 )`.
 
  ## Resources: 
 
+- [Language home](https://lynglang.com)
 - [introduction and tutorial](docs/tutorial.md) - start here please
+- [What's New in 1.5](docs/whats_new_1_5.md)
+- [Testing and Assertions](docs/Testing.md)
+- [Filesystem and Processes (lyngio)](docs/lyngio.md)
+- [Return Statement](docs/return_statement.md)
+- [Efficient Iterables in Kotlin Interop](docs/EfficientIterables.md)
 - [Samples directory](docs/samples)
+- [Formatter (core + CLI + IDE)](docs/formatter.md)
 - [Books directory](docs)
+- [AI agent guidance](AGENTS.md)
 
 ## Integration in Kotlin multiplatform
 
@@ -47,7 +64,7 @@ and it is multithreaded on platforms supporting it (automatically, no code chang
 
 ```kotlin
 // update to current please:
-val lyngVersion = "0.6.1-SNAPSHOT"
+val lyngVersion = "1.5.0-SNAPSHOT"
 
 repositories {
     // ...
@@ -71,7 +88,7 @@ Now you can import lyng and use it:
 ### Execute script:
 
 ```kotlin
-import net.sergeyh.lyng.*
+import net.sergeych.lyng.*
 
 // we need a coroutine to start, as Lyng
 // is a coroutine based language, async topdown
@@ -87,9 +104,7 @@ Script is executed over some `Scope`. Create instance,
 add your specific vars and functions to it, and call:
 
 ```kotlin
-
-import com.sun.source.tree.Scope
-import new.sergeych.lyng.*
+import net.sergeych.lyng.*
 
 // simple function
 val scope = Script.newScope().apply {
@@ -115,6 +130,34 @@ scope.eval("sumOf(1,2,3)") // <- 6
 ```
 Note that the scope stores all changes in it so you can make calls on a single scope to preserve state between calls.
 
+## IntelliJ IDEA plugin: Lightweight autocompletion (experimental)
+
+The IDEA plugin provides a fast, lightweight BASIC completion for Lyng code (IntelliJ IDEA 2024.3+).
+
+What it does:
+- Global suggestions: in-scope parameters, same-file declarations (functions/classes/vals), imported modules, and stdlib symbols.
+- Member completion after dot: offers only members of the inferred receiver type. It works for chained calls like `Path(".." ).lines().` (suggests `Iterator` methods), and for literals like `"abc".` (String methods) or `[1,2,3].` (List/Iterable methods).
+- Inheritance-aware: shows direct class members first, then inherited. For example, `List` also exposes common `Collection`/`Iterable` methods.
+- Static/namespace members: `Name.` lists only static members when `Name` is a known class or container (e.g., `Math`).
+- Performance: suggestions are capped; prefix filtering is early; parsing is cached; computation is cancellation-friendly.
+
+What it does NOT do (yet):
+- No heavy resolve or project-wide indexing. It’s best-effort, driven by a tiny MiniAst + built-in docs registry.
+- No control/data-flow type inference.
+
+Enable/disable:
+- Settings | Lyng Formatter → "Enable Lyng autocompletion (experimental)" (default: ON).
+
+Tips:
+- After a dot, globals are intentionally suppressed (e.g., `lines().Path` is not valid), only the receiver’s members are suggested.
+- If completion seems sparse, make sure related modules are imported (e.g., `import lyng.io.fs` so that `Path` and its methods are known).
+
+## AI Assistant Support
+
+To help AI assistants (like Cursor, Windsurf, or GitHub Copilot) understand Lyng with minimal effort, we provide a high-density language specification:
+
+- **[LYNG_AI_SPEC.md](LYNG_AI_SPEC.md)**: A concise guide for AI models to learn Lyng syntax, idioms, and core philosophy. We recommend pointing your AI tool to this file or including it in your project's custom instructions.
+
 ## Why? 
 
 Designed to add scripting to kotlin multiplatform application in easy and efficient way. This is attempt to achieve what Lua is for C/++.
@@ -134,21 +177,8 @@ Designed to add scripting to kotlin multiplatform application in easy and effici
 
 # Language Roadmap
 
-```mermaid
-flowchart
-    v0([the idea])
-    v1([v1: make it happen])
-    v2([v1.5: testmake it fasted and rich featured])
-    v3([v2: ideal script language])
-    v0 --code MVP--> v1
-    v1 --refine and extend--> v2
-    v2 -- optimize --> v3
-    
-```
-
-## v1.0.0 "Make it happen"
-
-Planned autumn 2025. Complete dynamic language with sufficient standard library:
+We are now at **v1.5.0-SNAPSHOT** (stable development cycle): basic optimization performed, battery included: standard library is 90% here, initial
+support in HTML, popular editors, and IDEA; tools to syntax highlight and format code are ready. It was released closed to schedule.
 
 Ready features:
 
@@ -159,6 +189,7 @@ Ready features:
 - [x] ranges, lists, strings, interfaces: Iterable, Iterator, Collection, Array
 - [x] when(value), if-then-else
 - [x] exception handling: throw, try-catch-finally, exception classes.
+- [x] user-defined exception classes
 - [x] multiplatform maven publication
 - [x] documentation for the current state
 - [x] maps, sets and sequences (flows?)
@@ -171,31 +202,45 @@ Ready features:
 - [x] dynamic fields
 - [x] function annotations
 - [x] better stack reporting
-
-###  Under way: 
-
 - [x] regular exceptions + extended `when`
 - [x] multiple inheritance for user classes
-- [ ] site with integrated interpreter to give a try
-- [ ] kotlin part public API good docs, integration focused
+- [x] class properties (accessors)
+- [x] `return` statement for local and non-local exit
+- [x] Unified Delegation model: val, var and fun
+- [x] `lazy val` using delegation
+- [x] singletons `object TheOnly { ... }`
+- [x] object expressions `object: List { ... }`
+- [x] late-init vals in classes
+- [x] properties with getters and setters
+- [x] assign-if-null operator `?=`
+- [x] user-defined exception classes
 
-## plan: v1.0 - v1.5 "Rich and stable"
+All of this is documented in the [language site](https://lynglang.com) and locally [docs/language.md](docs/tutorial.md). the current nightly builds published on the site and in the private maven repository.  
 
-Estimated spring of 2026
-
-Planned features.
+## plan: towards v2.0 Next Generation
 
+- [x] site with integrated interpreter to give a try
+- [x] kotlin part public API good docs, integration focused
 - [ ] type specifications
-- [ ] language server or compose-based lyng-aware editor
+- [x] Textmate Bundle
+- [x] IDEA plugin
 - [ ] source docs and maybe lyng.md to a standard
 - [ ] metadata first class access from lyng
+- [x] aggressive optimizations
+- [ ] compile to JVM bytecode optimization
 
 ## After 1.5 "Ideal scripting"
 
-Estimated winter 2027
+Estimated summer 2026
 
-- [ ] client with GUI support based on compose multiplatform somehow
-- [ ] notebook - style workbooks with graphs, formulae, etc.
-- [ ] aggressive optimizations
+- propose your feature! 
+
+## Authors
+
+@-links are for contacting authors on [project home](https://gitea.sergeych.net/SergeychWorks/lyng): this simplest s to open issue for the person you need to convey any information about this project.
+
+__Sergey Chernov__ @sergeych: Initial idea and architecture, language concept, design, implementation.
+
+__Yulia Nezhinskaya__ @AlterEgoJuliaN: System analysis, math and features design.
 
 [parallelism]: docs/parallelism.md

archived/README.md

@@ -0,0 +1,4 @@
+# Obsolete files
+
+
+__Do not rely on contents of the files in this directory. They are kept for historical reference only and may not be up-to-date or relevant.__

archived/development/String.md

@@ -1,3 +1,5 @@
+[//]: # (excludeFromIndex)
+
 # String
 
 # This document is for developer notes only

archived/development/including_modules.md

@@ -1,5 +1,7 @@
 # Modules inclusion
 
+[//]: # (excludeFromIndex)
+
 Module is, at the low level, a statement that modifies a given context by adding
 here local and exported symbols, performing some tasks and even returning some value
 we don't need for now.

archived/development/scope_resolution.md

@@ -1,3 +1,4 @@
+[//]: # (excludeFromIndex)
 
 
 Provide:

archived/proposals/delegates.lyng

@@ -0,0 +1,117 @@
+/*
+    This is a tech proposal under construction, please do not use it yet
+    for any purpose
+*/
+
+/*
+    Abstract delegate can be used to proxy read/wrtie field access
+    or method call. Default implementation reports error.
+*/
+interface Delegate {
+    fun getValue() = Unset
+    fun setValue(newValue) { throw NotImplementedException("delegate setter is not implemented") }
+    fun invoke(args...) { throw NotImplementedException("delegate setter is not implemented") }
+}
+
+/*
+    Delegate cam be used to implement a val, var or fun, so there are
+    access type enum to distinguish:
+*/
+enum DelegateAccess {
+    Val,
+    Var,
+    Callable
+}
+
+// Delegate can be associated by a val/var/fun in a declaraion site using `by` keyword
+
+val proxiedVal by proxy(1)
+var proxiedVar by proxy(2, 3)
+fun proxiedFun by proxy()
+
+// each proxy is a Lyng expression returning instance of the Proxy interface:
+
+/*
+    Proxy interface is connecting some named property of a given kind with the `Delegate`.
+    It removes the burden of dealing with property name and this ref on each get/set value
+    or invoke allowing having one delegate per instance, execution buff.
+*/
+interface Proxy {
+    fun getDelegate(propertyName: String,access: DelegateAccess,thisRef: Obj?): Delegate
+}
+
+// val, var and fun can be delegated, local or class instance:
+class TestProxy: Proxy {
+    override getDelegate(name,access,thisRef) {
+        Delegate()
+    }
+}
+
+val proxy = TestProxy()
+
+class Allowed {
+    val v1 by proxy
+    var v2 by proxy
+    fun f1 by proxy
+}
+val v3 by proxy
+var v4 by proxy
+fun f2 by proxy
+
+/*
+    It means that for example
+    Allowed().f1("foo")
+    would call a delegate.invoke("foo") on the `Delegate` instance supplied by `proxy`, etc.
+*/
+
+// The practic sample: lazy value
+
+/*
+    The delegate that caches single time evaluated value
+*/
+class LazyDelegate(creator): Delegate {
+    private var currentValue=Unset
+
+    override fun getValue() {
+        if( currentValue == Unset )
+            currentValue = creator()
+        currentValue
+    }
+}
+
+/*
+    The proxy to assign it
+*/
+class LazyProxy(creator) {
+    fun getDelegate(name,access,thisRef) {
+        if( access != DelegateAccess.Val )
+            throw IllegalArgumentException("only lazy val are allowed")
+        LazyDelegate(creator)
+    }
+}
+
+
+/*
+    A helper function to simplify creation:
+*/
+fun lazy(creator) {
+    LazyProxy(creator)
+}
+
+// Usage sample and the test:
+var callCounter = 0
+assertEquals(0, clallCounter)
+
+val lazyText by lazy { "evaluated text" }
+
+// the lazy property is not yet evaluated:
+assertEquals(0, clallCounter)
+// now evaluate it by using it:
+assertEquals("evaluated text", lazyText)
+assertEquals(1, callCounter)
+
+// lazy delegate should fail on vars or funs:
+assertThrows { var bad by lazy { "should not happen" } }
+assertThrows { fun bad by lazy { 42 } }
+
+

archived/proposals/map_literal.md

@@ -0,0 +1,95 @@
+
+# Map literals — refined proposal
+
+[//]: # (excludeFromIndex)
+
+Implement JavaScript-like literals for maps. The syntax and semantics align with named arguments in function calls, but map literals are expressions that construct `Map` values.
+
+Keys can be either:
+- string literals: `{ "some key": value }`, or
+- identifiers: `{ name: expr }`, where the key becomes the string `"name"`.
+
+Identifier shorthand inside map literals is supported:
+- `{ name: }` desugars to `{ "name": name }`.
+
+Property access sugar is not provided for maps: use bracket access only, e.g. `m["a"]`, not `m.a`.
+
+Examples:
+
+```lyng
+val x = 2
+val m = { "a": 1, x: x*10, y: }
+assertEquals(1, m["a"])      // string-literal key
+assertEquals(20, m["x"])     // identifier key
+assertEquals(2, m["y"])      // identifier shorthand
+```
+
+Spreads (splats) in map literals are allowed and merged left-to-right with “rightmost wins” semantics:
+
+```lyng
+val base = { a: 1, b: 2 }
+val m = { a: 0, ...base, b: 3, c: 4 }
+assertEquals(1, m["a"])  // base overwrites a:0
+assertEquals(3, m["b"])  // literal overwrites spread
+assertEquals(4, m["c"])  // new key
+```
+
+Trailing commas are allowed (optional):
+
+```lyng
+val m = {
+  "a": 1,
+  b: 2,
+  ...other,
+}
+```
+
+Duplicate keys among literal entries (including identifier shorthand) are a compile-time error:
+
+```lyng
+{ foo: 1, "foo": 2 }   // error: duplicate key "foo"
+{ foo:, foo: 2 }        // error: duplicate key "foo"
+```
+
+Spreads are evaluated at runtime. Overlaps from spreads are resolved by last write wins. If a spread is not a map, or yields a map with non-string keys, it’s a runtime error.
+
+Merging with `+`/`+=` and entries:
+
+```lyng
+("1" => 10) + ("2" => 20)     // Map("1"=>10, "2"=>20)
+{ "1": 10 } + ("2" => 20)     // same
+{ "1": 10 } + { "2": 20 }    // same
+
+var m = { "a": 1 }
+m += ("b" => 2)                 // m = { "a":1, "b":2 }
+```
+
+Rightmost wins on duplicates consistently across spreads and merges. All map merging operations require string keys; encountering a non-string key during merge is a runtime error.
+
+Empty map literal `{}` is not supported to avoid ambiguity with blocks/lambdas. Use `Map()` for an empty map.
+
+Lambda disambiguation
+- A `{ ... }` with typed lambda parameters must have a top-level `->` in its header. The compiler disambiguates by looking for a top-level `->`. If none is found, it attempts to parse a map literal; if that fails, it is parsed as a lambda or block.
+
+Grammar (EBNF)
+
+```
+ws                    = zero or more whitespace (incl. newline/comments)
+map_literal           = '{' ws map_entries ws '}'
+map_entries           = map_entry ( ws ',' ws map_entry )* ( ws ',' )?
+map_entry             = map_key ws ':' ws map_value_opt
+                      | '...' ws expression
+map_key               = string_literal | ID
+map_value_opt         = expression | ε   // ε allowed only if map_key is ID
+```
+
+Notes:
+- Identifier shorthand (`id:`) is allowed only for identifiers, not string-literal keys.
+- Spreads accept any expression; at runtime it must yield a `Map` with string keys.
+- Duplicate keys are detected at compile time among literal keys; spreads are merged at runtime with last-wins.
+
+Rationale
+- The `{ name: value }` style is familiar and ergonomic.
+- Disambiguation with lambdas leverages the required `->` in typed lambda headers.
+- Avoiding `m.a` sidesteps method/field shadowing and keeps semantics clear.
+

archived/proposals/named_args.md

@@ -0,0 +1,70 @@
+# Named arguments in calls
+
+[//]: # (excludeFromIndex)
+
+
+Extend function/method calls to allow setting arguments by name using colon syntax at call sites. This is especially convenient with many parameters and default values.
+
+Examples:
+
+```lyng
+    fun test(a="foo", b="bar", c="bazz") { [a, b, c] }
+
+    assertEquals(test(b: "b"), ["foo", "b", "bazz"])
+    assertEquals(test("a", c: "c"), ["a", "bar", "c"])
+```
+
+Rules:
+
+- Named arguments are optional. If named arguments are present, their order is not important.
+- Named arguments must follow positional arguments; positional arguments cannot follow named ones (the only exception is the syntactic trailing block outside parentheses, see below).
+- A named argument cannot reassign a parameter already set positionally.
+- If the last parameter is already assigned by a named argument (or named splat), the trailing-lambda rule must NOT apply: a following `{ ... }` after the call is an error.
+
+Rationale for using `:` instead of `=` in calls: in Lyng, assignment `=` is an expression; using `:` avoids ambiguity and keeps declarations (`name: Type`) distinct from call sites, where casting uses `as` / `as?`.
+
+Migration note: earlier drafts/examples used `name = value`. The final syntax is `name: value` at call sites.
+
+## Extended call argument splats: named splats
+
+With named arguments, splats (`...`) are extended to support maps as named splats. When a splat evaluates to a Map, its entries provide name→value assignments:
+
+```lyng
+    fun test(a="a", b="b", c="c", d="d") { [a, b, c, d] }
+
+    assertEquals(test("A?", ...Map("d" => "D!", "b" => "B!")), ["A?", "B!", "c", "D!"])
+```
+
+Constraints for named splats:
+
+- Only string keys are allowed in map splats; otherwise, a clean error is thrown.
+- Named splats cannot reassign parameters already set (positionally or by earlier named arguments/splats).
+- Named splats follow the same ordering as named arguments: they must appear after all positional arguments and positional splats.
+
+## Trailing-lambda interaction
+
+Lyng supports a syntactic trailing block after a call: `f(args) { ... }`. With named args/splats, if the last parameter is already assigned by name, the trailing block must not apply and the call is an error:
+
+```lyng
+    fun f(x, onDone) { onDone(x) }
+    f(x: 1) { 42 }    // ERROR: last parameter already assigned by name
+    f(1) { 42 }       // OK
+```
+
+## Errors (non-exhaustive)
+
+- Positional argument after any named argument inside parentheses: error.
+- Positional splat after any named argument: error.
+- Duplicate named assignment (directly or via map splats): error.
+- Unknown parameter name in a named argument/splat: error.
+- Map splat with non-string keys: error.
+- Attempt to target the ellipsis parameter by name: error.
+
+## Notes
+
+- Declarations continue to use `:` for types, while call sites use `:` for named arguments and `as` / `as?` for type casts/checks.
+
+
+
+
+

bin/deploy_all

@@ -0,0 +1,39 @@
+#!/bin/bash
+
+#
+# Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+#
+
+set -e
+echo "publishing all artifacts"
+echo
+./gradlew publishToMavenLocal site:jsBrowserDistribution publish buildInstallablePlugin :lyng:linkReleaseExecutableLinuxX64 :lyng:installJvmDist --parallel
+
+#echo
+#echo "Creating plugin"
+#echo
+#./gradlew buildInstallablePlugin
+
+echo
+echo "building CLI tools"
+echo
+bin/local_jrelease
+bin/local_release
+
+echo
+echo "Deploying site"
+echo
+./bin/deploy_site

bin/deploy_plugin

@@ -0,0 +1,26 @@
+#!/bin/sh
+
+#
+# Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+#
+
+set -e
+
+echo
+echo "Creating plugin"
+echo
+./gradlew buildInstallablePlugin
+deploy_site -u

bin/deploy_site

@@ -0,0 +1,189 @@
+#!/bin/bash
+
+#
+# Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+#
+
+upload_only=false
+for arg in "$@"; do
+  if [[ "$arg" == "-u" || "$arg" == "--upload-only" ]]; then
+    upload_only=true
+    break
+  fi
+done
+
+function checkState() {
+  if [[ $? != 0 ]]; then
+    echo
+    echo -- rsync failed. deploy was not finished. deployed version has not been affected
+    echo
+    exit 100
+  fi
+}
+
+
+
+# Update docs/idea_plugin.md to point to the latest built IDEA plugin zip
+# from ./distributables before building the site. The change is temporary and
+# the original file is restored right after the build.
+DOC_IDEA_PLUGIN="docs/idea_plugin.md"
+DOC_IDEA_PLUGIN_BACKUP="${DOC_IDEA_PLUGIN}.deploy_backup"
+
+function updateIdeaPluginDownloadLink() {
+  if [[ ! -f "$DOC_IDEA_PLUGIN" ]]; then
+    echo "WARN: $DOC_IDEA_PLUGIN not found; skipping plugin link update"
+    return 0
+  fi
+
+  # Find the most recently modified plugin zip
+  local latest
+  latest=$(ls -t distributables/lyng-idea-*.zip 2>/dev/null | head -n 1)
+  if [[ -z "$latest" ]]; then
+    echo "WARN: no distributables/lyng-idea-*.zip found; leaving $DOC_IDEA_PLUGIN unchanged"
+    return 0
+  fi
+
+  local base
+  base=$(basename "$latest")
+  local version
+  version="${base#lyng-idea-}"
+  version="${version%.zip}"
+  local url
+  url="https://lynglang.com/distributables/${base}"
+  local newline
+  newline="### [Download plugin v${version}](${url})"
+
+  # Backup and rewrite the specific markdown line if present
+  cp "$DOC_IDEA_PLUGIN" "$DOC_IDEA_PLUGIN_BACKUP" || {
+    echo "ERROR: can't backup $DOC_IDEA_PLUGIN"; return 1; }
+
+  # Replace the line that starts with the download header; if not found, append it
+  awk -v repl="$newline" 'BEGIN{done=0} \
+    /^### \[Download plugin v/ { print repl; done=1; next } \
+    { print } \
+    END { if (done==0) exit 42 }' "$DOC_IDEA_PLUGIN_BACKUP" > "$DOC_IDEA_PLUGIN"
+
+  local rc=$?
+  if [[ $rc -eq 42 ]]; then
+    echo "WARN: download link not found in $DOC_IDEA_PLUGIN; appending generated link"
+    echo >> "$DOC_IDEA_PLUGIN"
+    echo "$newline" >> "$DOC_IDEA_PLUGIN"
+  elif [[ $rc -ne 0 ]]; then
+    echo "ERROR: failed to update $DOC_IDEA_PLUGIN; restoring original"
+    mv -f "$DOC_IDEA_PLUGIN_BACKUP" "$DOC_IDEA_PLUGIN" 2>/dev/null
+    return 1
+  fi
+}
+
+# default target settings
+case "com" in
+  com)
+    SSH_HOST=sergeych@d.lynglang.com # host to deploy to
+    SSH_PORT=22                             # ssh port on it
+    ROOT=/bigstore/sergeych_pub/lyng                 # directory to rsync to
+    ;;
+#  com)
+#    SSH_HOST=vvk@front-01.neurodatalab.com
+#    ROOT=/home/vvk
+#    ;;
+  *)
+    echo "*** ERROR: target not specified (use deploy com | dev)"
+    echo "*** stop"
+    exit 101
+esac
+
+die() { echo "ERROR: $*" 1>&2 ; exit 1; }
+
+function refreshTextmateZip() {
+  echo "Refreshing distributables/lyng-textmate.zip from editors/..."
+  mkdir -p distributables
+  # We use -r for recursive and -q for quiet (optional)
+  # -j can be used if we want to junk paths, but the request says "contents of editors/"
+  # usually we want to preserve the structure inside editors/
+  (cd editors && zip -rq ../distributables/lyng-textmate.zip .)
+}
+
+
+if [[ "$upload_only" == false ]]; then
+  # Update the IDEA plugin download link in docs (temporarily), then build, then restore the doc
+  refreshTextmateZip
+  updateIdeaPluginDownloadLink || echo "WARN: proceeding without updating IDEA plugin download link"
+
+  ./gradlew site:jsBrowserDistribution
+  BUILD_RC=$?
+
+  # Always restore original doc if backup exists
+  if [[ -f "$DOC_IDEA_PLUGIN_BACKUP" ]]; then
+    mv -f "$DOC_IDEA_PLUGIN_BACKUP" "$DOC_IDEA_PLUGIN"
+  fi
+
+  if [[ $BUILD_RC -ne 0 ]]; then
+    echo
+    echo -- build failed. deploy aborted.
+    echo
+    exit 100
+  fi
+fi
+
+# Prepare working dir
+ssh -p ${SSH_PORT} ${SSH_HOST} "
+  cd ${ROOT}
+  rm -rd build 2>/dev/null
+  if [ -d release ]; then
+    echo copying current release
+    cp -r release build
+  else
+    echo creating first release
+    mkdir release
+    mkdir build
+  fi
+";
+
+if [[ "$upload_only" == false ]]; then
+  # sync files
+  SRC=./site/build/dist/js/productionExecutable
+  rsync -e "ssh -p ${SSH_PORT}" -avz -r -d --delete ${SRC}/* ${SSH_HOST}:${ROOT}/build/dist
+  checkState
+  #rsync -e "ssh -p ${SSH_PORT}" -avz  ./static/* ${SSH_HOST}:${ROOT}/build/dist
+  #checkState
+fi
+
+rsync -e "ssh -p ${SSH_PORT}" -avz -r -d --delete distributables/* ${SSH_HOST}:${ROOT}/build/dist/distributables
+checkState
+
+echo
+echo finalizing the deploy...
+ssh -p ${SSH_PORT} ${SSH_HOST} "
+  cd ${ROOT}
+  rm -rd release~
+  mv release release~
+  mv build release
+  cd release
+  # in this project we needn't restart back when we deploy the front
+  #  ~/bin/restart_service
+";
+
+if [[ $? != 0 ]]; then
+  echo
+  echo -- finalization failed. the rease might be corrupt. rolling back is not yet implemented.
+  echo
+  exit 100
+fi
+
+echo
+echo Deploy successful
+echo
+

bin/generate_docs.sh

@@ -0,0 +1,256 @@
+#!/bin/bash
+#
+# Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+#
+
+set -e
+
+# Configuration
+DOCS_DIR="docs"
+OUTPUT_DIR="distributables"
+TEMP_DIR="build/temp_docs"
+MERGED_MD="$TEMP_DIR/merged.md"
+OUTPUT_HTML="$OUTPUT_DIR/lyng_documentation.html"
+
+mkdir -p "$OUTPUT_DIR"
+mkdir -p "$TEMP_DIR"
+
+# Files that should come first in specific order
+PRIORITY_FILES=(
+    "tutorial.md"
+    "OOP.md"
+    "advanced_topics.md"
+    "declaring_arguments.md"
+    "scopes_and_closures.md"
+    "exceptions_handling.md"
+    "when.md"
+    "parallelism.md"
+    "Testing.md"
+)
+
+# Files that should come next (reference)
+REFERENCE_FILES=(
+    "Collection.md"
+    "Iterable.md"
+    "Iterator.md"
+    "List.md"
+    "Set.md"
+    "Map.md"
+    "Array.md"
+    "Buffer.md"
+    "RingBuffer.md"
+    "Range.md"
+    "Real.md"
+    "Regex.md"
+    "math.md"
+    "time.md"
+)
+
+# Files that are about integration/tools
+INTEGRATION_FILES=(
+    "serialization.md"
+    "json_and_kotlin_serialization.md"
+    "embedding.md"
+    "lyng_cli.md"
+    "lyng.io.fs.md"
+    "formatter.md"
+    "EfficientIterables.md"
+)
+
+# Tracking processed files to avoid duplicates
+PROCESSED_PATHS=()
+
+is_excluded() {
+    local full_path="$1"
+    if grep -q "excludeFromIndex" "$full_path"; then
+        return 0 # true in bash
+    fi
+    return 1 # false
+}
+
+process_file() {
+    local rel_path="$1"
+    local full_path="$DOCS_DIR/$rel_path"
+    
+    if [[ ! -f "$full_path" ]]; then
+        return
+    fi
+    
+    if is_excluded "$full_path"; then
+        echo "Skipping excluded: $rel_path"
+        return
+    fi
+
+    # Check for duplicates
+    for p in "${PROCESSED_PATHS[@]}"; do
+        if [[ "$p" == "$rel_path" ]]; then
+            return
+        fi
+    done
+    PROCESSED_PATHS+=("$rel_path")
+
+    echo "Processing: $rel_path"
+    
+    # 1. Add an anchor for the file based on its path
+    local anchor_name=$(echo "$rel_path" | sed 's/\//_/g')
+    echo "<div id=\"$anchor_name\"></div>" >> "$MERGED_MD"
+    echo "" >> "$MERGED_MD"
+    
+    # 2. Append content with fixed links
+    # - [text](file.md) -> [text](#file.md)
+    # - [text](dir/file.md) -> [text](#dir_file.md)
+    # - [text](file.md#anchor) -> [text](#anchor)
+    # - Fix image links: [alt](../images/...) -> [alt](images/...) if needed, but none found yet.
+    
+    cat "$full_path" | \
+    perl -pe 's/\[([^\]]+)\]\(([^)]+)\.md\)/"[$1](#" . ($2 =~ s|\/|_|gr) . ".md)"/ge' | \
+    perl -pe 's/\[([^\]]+)\]\(([^)]+)\.md#([^)]+)\)/[$1](#$3)/g' >> "$MERGED_MD"
+    
+    echo -e "\n\n---\n\n" >> "$MERGED_MD"
+}
+
+# Start with an empty merged file
+echo "% Lyng Language Documentation" > "$MERGED_MD"
+echo "" >> "$MERGED_MD"
+
+# 1. Process priority files
+for f in "${PRIORITY_FILES[@]}"; do
+    process_file "$f"
+done
+
+# 2. Process reference files
+for f in "${REFERENCE_FILES[@]}"; do
+    process_file "$f"
+done
+
+# 3. Process integration files
+for f in "${INTEGRATION_FILES[@]}"; do
+    process_file "$f"
+done
+
+# 4. Process remaining files in docs root
+for f in "$DOCS_DIR"/*.md; do
+    rel_f=${f#"$DOCS_DIR/"}
+    process_file "$rel_f"
+done
+
+# 5. Process remaining files in subdirs (like samples)
+find "$DOCS_DIR" -name "*.md" | sort | while read -r f; do
+    rel_f=${f#"$DOCS_DIR/"}
+    process_file "$rel_f"
+done
+
+echo "Running pandoc to generate $OUTPUT_HTML..."
+
+# Use a basic but clean CSS
+pandoc "$MERGED_MD" -o "$OUTPUT_HTML" \
+    --toc --toc-depth=2 \
+    --standalone \
+    --embed-resources \
+    --metadata title="Lyng Language Documentation" \
+    --css <(echo "
+        body { 
+            font-family: -apple-system, BlinkMacSystemFont, \"Segoe UI\", Helvetica, Arial, sans-serif;
+            line-height: 1.6; 
+            max-width: 1000px; 
+            margin: 0 auto; 
+            padding: 2em; 
+            color: #24292e;
+            background-color: #fff;
+        }
+        code { 
+            background-color: rgba(27,31,35,0.05); 
+            padding: 0.2em 0.4em; 
+            border-radius: 3px; 
+            font-family: SFMono-Regular, Consolas, \"Liberation Mono\", Menlo, monospace;
+            font-size: 85%;
+        }
+        pre { 
+            background-color: #f6f8fa; 
+            padding: 16px; 
+            overflow: auto; 
+            border-radius: 3px;
+            line-height: 1.45;
+        }
+        pre code {
+            background-color: transparent;
+            padding: 0;
+            font-size: 100%;
+        }
+        h1 { 
+            border-bottom: 1px solid #eaecef; 
+            padding-bottom: 0.3em; 
+            margin-top: 24px;
+            margin-bottom: 16px;
+            font-weight: 600;
+        }
+        h2 { 
+            border-bottom: 1px solid #eaecef; 
+            padding-bottom: 0.3em; 
+            margin-top: 24px;
+            margin-bottom: 16px;
+            font-weight: 600;
+        }
+        hr { 
+            height: 0.25em;
+            padding: 0;
+            margin: 24px 0;
+            background-color: #e1e4e8;
+            border: 0;
+        }
+        blockquote {
+            padding: 0 1em;
+            color: #6a737d;
+            border-left: 0.25em solid #dfe2e5;
+            margin: 0 0 16px 0;
+        }
+        nav#TOC { 
+            background: #f9f9f9; 
+            padding: 1em; 
+            border: 1px solid #eee; 
+            margin-bottom: 2.5em; 
+            border-radius: 6px;
+        }
+        nav#TOC ul { 
+            list-style: none; 
+            padding-left: 1.5em; 
+        }
+        nav#TOC > ul {
+            padding-left: 0;
+        }
+        table {
+            border-spacing: 0;
+            border-collapse: collapse;
+            margin-top: 0;
+            margin-bottom: 16px;
+        }
+        table th, table td {
+            padding: 6px 13px;
+            border: 1px solid #dfe2e5;
+        }
+        table tr {
+            background-color: #fff;
+            border-top: 1px solid #c6cbd1;
+        }
+        table tr:nth-child(2n) {
+            background-color: #f6f8fa;
+        }
+    ")
+
+echo "-------------------------------------------------------"
+echo "Done! Documentation generated successfully."
+echo "Location: $OUTPUT_HTML"
+echo "-------------------------------------------------------"

bin/local_release

@@ -25,3 +25,6 @@ file=./lyng/build/bin/linuxX64/releaseExecutable/lyng.kexe
 strip $file
 upx   $file
 cp $file ~/bin/lyng
+cp $file ./distributables/lyng
+zip ./distributables/lyng-linuxX64 ./distributables/lyng
+rm ./distributables/lyng

build.gradle.kts

@@ -1,5 +1,5 @@
 /*
- * Copyright 2025 Sergey S. Chernov real.sergeych@gmail.com
+ * Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,3 +20,42 @@ plugins {
     alias(libs.plugins.kotlinMultiplatform) apply  false
     alias(libs.plugins.vanniktech.mavenPublish) apply false
 }
+
+// Convenience alias to run the IntelliJ IDE with the Lyng plugin from the project root.
+// Usage: ./gradlew runIde
+// It simply delegates to :lyng-idea:runIde provided by the Gradle IntelliJ Plugin.
+tasks.register<org.gradle.api.DefaultTask>("runIde") {
+    group = "intellij"
+    description = "Run IntelliJ IDEA with the Lyng plugin (:lyng-idea)"
+    dependsOn(":lyng-idea:runIde")
+}
+
+tasks.register<Exec>("generateDocs") {
+    group = "documentation"
+    description = "Generates a single-file documentation HTML using bin/generate_docs.sh"
+    commandLine("./bin/generate_docs.sh")
+}
+
+// Sample generator task for .lyng.d definition files (not wired into build).
+// Usage: ./gradlew generateLyngDefsSample
+tasks.register("generateLyngDefsSample") {
+    group = "lyng"
+    description = "Generate a sample .lyng.d file under build/generated/lyng/defs"
+    outputs.dir(layout.buildDirectory.dir("generated/lyng/defs"))
+    doLast {
+        val outDir = layout.buildDirectory.dir("generated/lyng/defs").get().asFile
+        outDir.mkdirs()
+        val outFile = outDir.resolve("sample.lyng.d")
+        outFile.writeText(
+            """
+            /** Generated API */
+            extern fun ping(): Int
+
+            /** Generated class */
+            class Generated(val name: String) {
+                fun greet(): String = "hi " + name
+            }
+            """.trimIndent()
+        )
+    }
+}

bytecode_migration_plan.md

@@ -0,0 +1,7 @@
+# Bytecode Migration Plan (Archived)
+
+Status: completed.
+
+Historical reference:
+- `notes/archive/bytecode_migration_plan.md` (full plan)
+- `notes/archive/bytecode_migration_plan_completed.md` (summary)

docs/Array.md

@@ -1,8 +1,8 @@
 # Array
 
 It's an interface if the [Collection] that provides indexing access, like `array[3] = 0`.
-Array therefore implements [Iterable] too. The well known implementatino of the `Array` is
-[List].
+Array therefore implements [Iterable] too. Well known implementations of `Array` are
+[List] and [ImmutableList].
 
 Array adds the following methods:
 
@@ -35,3 +35,4 @@ To pre-sort and array use `Iterable.sorted*` or in-place `List.sort*` families,
 [Collection]: Collection.md
 [Iterable]: Iterable.md
 [List]: List.md
+[ImmutableList]: ImmutableList.md

docs/Buffer.md

@@ -23,11 +23,11 @@ There are a lo of ways to construct a buffer:
     assertEquals( 5, Buffer("hello").size )
 
     // from bytes, e.g. integers in range 0..255
-    assertEquals( 255, Buffer(1,2,3,255).last() )
+    assertEquals( 255, Buffer(1,2,3,255).last )
 
     // from whatever iterable that produces bytes, e.g.
     // integers in 0..255 range:
-    assertEquals( 129, Buffer([1,2,129]).last() )
+    assertEquals( 129, Buffer([1,2,129]).last )
 
     // Empty buffer of fixed size:
     assertEquals(100, Buffer(100).size)

docs/BytecodeSpec.md

@@ -0,0 +1,280 @@
+# Lyng Bytecode VM Spec v0 (Draft)
+
+This document describes a register-like (3-address) bytecode for Lyng with
+dynamic slot width (8/16/32-bit slot IDs), a slot-tail argument model, and
+typed lanes for Obj/Int/Real/Bool. The VM is intended to run as a suspendable
+interpreter and fall back to the existing AST execution when needed.
+
+## 1) Frame & Slot Model
+
+### Frame metadata
+- localCount: number of local slots for this function (fixed at compile time).
+- argCount: number of arguments passed at call time.
+- scopeSlotNames: optional debug names for scope slots (locals/params), aligned to slot mapping.
+- argBase = localCount.
+
+### Slot layout
+slots[0 .. localCount-1]              locals
+slots[localCount .. localCount+argCount-1]  arguments
+
+### Typed lanes
+- slotType[]: UNKNOWN/OBJ/INT/REAL/BOOL
+- objSlots[], intSlots[], realSlots[], boolSlots[]
+- A slot is a logical index; active lane is selected by slotType.
+
+### Parameter access
+- param i => slot localCount + i
+- variadic extra => slot localCount + declaredParamCount + k
+
+### Debug metadata (optional)
+- scopeSlotNames: array sized scopeSlotCount, each entry nullable.
+- Intended for disassembly/debug tooling; VM semantics do not depend on it.
+
+### Constant pool extras
+- SlotPlan: map of name -> slot index, used by PUSH_SCOPE to pre-allocate and map loop locals.
+- CallArgsPlan: ordered argument specs (name/splat) + tailBlock flag, used when argCount has the plan flag set.
+
+## 2) Slot ID Width
+
+Per frame, select:
+- 8-bit if localCount + argCount < 256
+- 16-bit if < 65536
+- 32-bit otherwise
+
+The decoder uses a dedicated loop per width. All slot operands are expanded to
+Int internally.
+
+## 3) CALL Semantics (Model A)
+
+Instruction:
+CALL_DIRECT fnId, argBase, argCount, dst
+
+Behavior:
+- Allocate a callee frame sized localCount + argCount.
+- Copy caller slots [argBase .. argBase+argCount-1] into callee slots
+  [localCount .. localCount+argCount-1].
+- Callee returns via RET slot or RET_VOID.
+- Caller stores return value to dst.
+
+Other calls:
+- CALL_VIRTUAL recvSlot, methodId, argBase, argCount, dst
+- CALL_FALLBACK stmtId, argBase, argCount, dst
+- CALL_SLOT calleeSlot, argBase, argCount, dst
+
+## 4) Binary Encoding Layout
+
+All instructions are:
+  [opcode:U8] [operands...]
+
+Operand widths:
+- slotId: S = 1/2/4 bytes (per frame slot width)
+- constId: K = 2 bytes (U16), extend to 4 if needed
+- ip: I = 2 bytes (U16) or 4 bytes (U32) per function size
+- fnId/methodId/stmtId: F/M/T = 2 bytes (U16) unless extended
+- argCount: C = 2 bytes (U16), extend to 4 if needed
+
+Endianness: little-endian for multi-byte operands.
+
+Common operand patterns:
+- S: one slot
+- SS: two slots
+- SSS: three slots
+- K S: constId + dst slot
+- S I: slot + jump target
+- I: jump target
+- F S C S: fnId, argBase slot, argCount, dst slot
+
+Arg count flag:
+- If high bit of C is set (0x8000), the low 15 bits encode a CallArgsPlan constId.
+- When not set, C is the raw positional count and tailBlockMode=false.
+
+## 5) Opcode Table
+
+Note: Any opcode can be compiled to FALLBACK if not implemented in a VM pass.
+
+### Data movement
+- NOP
+- MOVE_OBJ S -> S
+- MOVE_INT S -> S
+- MOVE_REAL S -> S
+- MOVE_BOOL S -> S
+- BOX_OBJ S -> S
+- CONST_OBJ K -> S
+- CONST_INT K -> S
+- CONST_REAL K -> S
+- CONST_BOOL K -> S
+- CONST_NULL -> S
+
+### Numeric conversions
+- INT_TO_REAL S -> S
+- REAL_TO_INT S -> S
+- BOOL_TO_INT S -> S
+- INT_TO_BOOL S -> S
+
+### Arithmetic: INT
+- ADD_INT S, S -> S
+- SUB_INT S, S -> S
+- MUL_INT S, S -> S
+- DIV_INT S, S -> S
+- MOD_INT S, S -> S
+- NEG_INT S -> S
+- INC_INT S
+- DEC_INT S
+
+### Arithmetic: REAL
+- ADD_REAL S, S -> S
+- SUB_REAL S, S -> S
+- MUL_REAL S, S -> S
+- DIV_REAL S, S -> S
+- NEG_REAL S -> S
+
+### Arithmetic: OBJ
+- ADD_OBJ S, S -> S
+- SUB_OBJ S, S -> S
+- MUL_OBJ S, S -> S
+- DIV_OBJ S, S -> S
+- MOD_OBJ S, S -> S
+
+### Bitwise: INT
+- AND_INT S, S -> S
+- OR_INT S, S -> S
+- XOR_INT S, S -> S
+- SHL_INT S, S -> S
+- SHR_INT S, S -> S
+- USHR_INT S, S -> S
+- INV_INT S -> S
+
+### Comparisons (typed)
+- CMP_EQ_INT S, S -> S
+- CMP_NEQ_INT S, S -> S
+- CMP_LT_INT S, S -> S
+- CMP_LTE_INT S, S -> S
+- CMP_GT_INT S, S -> S
+- CMP_GTE_INT S, S -> S
+- CMP_EQ_REAL S, S -> S
+- CMP_NEQ_REAL S, S -> S
+- CMP_LT_REAL S, S -> S
+- CMP_LTE_REAL S, S -> S
+- CMP_GT_REAL S, S -> S
+- CMP_GTE_REAL S, S -> S
+- CMP_EQ_BOOL S, S -> S
+- CMP_NEQ_BOOL S, S -> S
+
+### Mixed numeric comparisons
+- CMP_EQ_INT_REAL S, S -> S
+- CMP_EQ_REAL_INT S, S -> S
+- CMP_LT_INT_REAL S, S -> S
+- CMP_LT_REAL_INT S, S -> S
+- CMP_LTE_INT_REAL S, S -> S
+- CMP_LTE_REAL_INT S, S -> S
+- CMP_GT_INT_REAL S, S -> S
+- CMP_GT_REAL_INT S, S -> S
+- CMP_GTE_INT_REAL S, S -> S
+- CMP_GTE_REAL_INT S, S -> S
+- CMP_NEQ_INT_REAL S, S -> S
+- CMP_NEQ_REAL_INT S, S -> S
+- CMP_EQ_OBJ S, S -> S
+- CMP_NEQ_OBJ S, S -> S
+- CMP_REF_EQ_OBJ S, S -> S
+- CMP_REF_NEQ_OBJ S, S -> S
+- CMP_LT_OBJ S, S -> S
+- CMP_LTE_OBJ S, S -> S
+- CMP_GT_OBJ S, S -> S
+- CMP_GTE_OBJ S, S -> S
+
+### Boolean ops
+- NOT_BOOL S -> S
+- AND_BOOL S, S -> S
+- OR_BOOL S, S -> S
+
+### Control flow
+- JMP I
+- JMP_IF_TRUE S, I
+- JMP_IF_FALSE S, I
+- RET S
+- RET_VOID
+- PUSH_SCOPE K
+- POP_SCOPE
+
+### Scope setup
+- PUSH_SCOPE uses const `SlotPlan` (name -> slot index) to create a child scope and apply slot mapping.
+- POP_SCOPE restores the parent scope.
+
+### Calls
+- CALL_DIRECT F, S, C, S
+- CALL_VIRTUAL S, M, S, C, S
+- CALL_FALLBACK T, S, C, S
+- CALL_SLOT S, S, C, S
+
+### Object access (optional, later)
+- GET_FIELD S, M -> S
+- SET_FIELD S, M, S
+- GET_INDEX S, S -> S
+- SET_INDEX S, S, S
+
+### Fallback
+- EVAL_FALLBACK T -> S
+
+## 6) Const Pool Encoding (v0)
+
+Each const entry is encoded as:
+  [tag:U8] [payload...]
+
+Tags:
+- 0x00: NULL
+- 0x01: BOOL (payload: U8 0/1)
+- 0x02: INT (payload: S64, little-endian)
+- 0x03: REAL (payload: F64, IEEE-754, little-endian)
+- 0x04: STRING (payload: U32 length + UTF-8 bytes)
+- 0x05: OBJ_REF (payload: U32 index into external Obj table)
+
+Notes:
+- OBJ_REF is reserved for embedding prebuilt Obj handles if needed.
+- Strings use UTF-8; length is bytes, not chars.
+
+## 7) Function Header (binary container)
+
+Suggested layout for a bytecode function blob:
+- magic: U32 ("LYBC")
+- version: U16 (0x0001)
+- slotWidth: U8 (1,2,4)
+- ipWidth: U8 (2,4)
+- constIdWidth: U8 (2,4)
+- localCount: U32
+- codeSize: U32 (bytes)
+- constCount: U32
+- constPool: [const entries...]
+- code: [bytecode...]
+
+Const pool entries use the encoding described in section 6.
+
+## 8) Sample Bytecode (illustrative)
+
+Example Lyng:
+  val x = 2
+  val y = 3
+  val z = x + y
+
+Assume:
+- localCount = 3 (x,y,z)
+- argCount = 0
+- slot width = 1 byte
+- const pool: [INT 2, INT 3]
+
+Bytecode:
+  CONST_INT k0 -> s0
+  CONST_INT k1 -> s1
+  ADD_INT s0, s1 -> s2
+  RET_VOID
+
+Encoded (opcode values symbolic):
+  [OP_CONST_INT][k0][s0]
+  [OP_CONST_INT][k1][s1]
+  [OP_ADD_INT][s0][s1][s2]
+  [OP_RET_VOID]
+
+## 9) Notes
+
+- Mixed-mode is allowed: compiler can emit FALLBACK ops for unsupported nodes.
+- The VM must be suspendable; on suspension, store ip + minimal operand state.
+- Source mapping uses a separate ip->Pos table, not part of core bytecode.

docs/Collection.md

@@ -6,14 +6,26 @@ Is a [Iterable] with known `size`, a finite [Iterable]:
         val size
     }
 
+`Collection` is a read/traversal contract shared by mutable and immutable collections.
+Concrete collection classes:
+
+- Mutable: [List], [Set], [Map]
+- Immutable: [ImmutableList], [ImmutableSet], [ImmutableMap]
+- Observable mutable lists (opt-in module): [ObservableList]
+
 | name                   | description                                          |
 |------------------------|------------------------------------------------------|
 
 (1)
 : `comparator(a,b)` should return -1 if `a < b`, +1 if `a > b` or zero.
 
-See [List], [Set] and [Iterable]
+See [List], [Set], [Iterable] and [Efficient Iterables in Kotlin Interop](EfficientIterables.md)
 
 [Iterable]: Iterable.md
 [List]: List.md
 [Set]: Set.md
+[Map]: Map.md
+[ImmutableList]: ImmutableList.md
+[ImmutableSet]: ImmutableSet.md
+[ImmutableMap]: ImmutableMap.md
+[ObservableList]: ObservableList.md

docs/EfficientIterables.md

@@ -0,0 +1,92 @@
+# Efficient Iterables in Kotlin Interop
+
+Lyng provides high-performance iteration mechanisms that allow Kotlin-side code to interact with Lyng iterables efficiently and vice versa.
+
+## 1. Enumerating Lyng Objects from Kotlin
+
+To iterate over a Lyng object (like a `List`, `Set`, or `Range`) from Kotlin code, use the virtual `enumerate` method:
+
+```kotlin
+val lyngList: Obj = ... 
+lyngList.enumerate(scope) { item ->
+    println("Processing $item")
+    true // return true to continue, false to break
+}
+```
+
+### Why it's efficient:
+- **Zero allocation**: Unlike traditional iterators, it doesn't create a `LyngIterator` object or any intermediate wrappers.
+- **Direct access**: Subclasses like `ObjList` override `enumerate` to iterate directly over their internal Kotlin collections.
+- **Reduced overhead**: It avoids multiple `invokeInstanceMethod` calls for `hasNext()` and `next()` on every step, which would normally involve dynamic dispatch and scope overhead.
+
+## 2. Reactive Enumeration with Flow
+
+If you prefer a reactive approach or need to integrate with Kotlin Coroutines flows, use `toFlow()`:
+
+```kotlin
+lyngList.toFlow(scope).collect { item ->
+    // ...
+}
+```
+*Note: `toFlow()` internally uses the Lyng iterator protocol (`iterator()`, `hasNext()`, `next()`), so it's slightly less efficient than `enumerate()` for performance-critical loops, but more idiomatic for flow-based processing.*
+
+## 3. Creating Efficient Iterables for Lyng in Kotlin
+
+When implementing a custom object in Kotlin that should be iterable in Lyng (e.g., usable in `for (x in myObj) { ... }`), follow these steps to ensure maximum performance.
+
+### A. Inherit from `Obj` and use `ObjIterable`
+Ensure your object's class has `ObjIterable` as a parent so the Lyng compiler recognizes it as an iterable.
+
+```kotlin
+class MyCollection(val items: List<Obj>) : Obj() {
+    override val objClass = MyCollection.type
+
+    companion object {
+        val type = ObjClass("MyCollection", ObjIterable).apply {
+            // Provide a Lyng-side iterator for compatibility with 
+            // manual iterator usage in Lyng scripts.
+            // Using ObjKotlinObjIterator if items are already Obj instances:
+            addFn("iterator") { 
+                ObjKotlinObjIterator(thisAs<MyCollection>().items.iterator()) 
+            }
+        }
+    }
+}
+```
+
+### B. Override `enumerate` for Maximum Performance
+The Lyng compiler's `for` loops use the `enumerate` method. By overriding it in your Kotlin class, you provide a "fast path" for iteration.
+
+```kotlin
+class MyCollection(val items: List<Obj>) : Obj() {
+    // ...
+    override suspend fun enumerate(scope: Scope, callback: suspend (Obj) -> Boolean) {
+        for (item in items) {
+            // If callback returns false, it means 'break' was called in Lyng
+            if (!callback(item)) break
+        }
+    }
+}
+```
+
+### C. Use `ObjInt.of()` for Numeric Data
+If your iterable contains integers, always use `ObjInt.of(Long)` instead of the `ObjInt(Long)` constructor. Lyng maintains a cache for small integers (-128 to 127), which significantly reduces object allocations and GC pressure during tight loops.
+
+```kotlin
+// Efficiently creating an integer object
+val obj = ObjInt.of(42L) 
+
+// Or using extension methods which also use the cache:
+val obj2 = 42.toObj()
+val obj3 = 42L.toObj()
+```
+
+#### Note on `toObj()` extensions:
+While `<reified T> T.toObj()` is convenient, using specific extensions like `Int.toObj()` or `Long.toObj()` is slightly more efficient as they use the `ObjInt` cache.
+
+## 4. Summary of Best Practices
+
+- **To Consume**: Use `enumerate(scope) { item -> ... true }`.
+- **To Implement**: Override `enumerate` in your `Obj` subclass.
+- **To Register**: Use `ObjIterable` (or `ObjCollection`) as a parent class in your `ObjClass` definition.
+- **To Optimize**: Use `ObjInt.of()` (or `.toObj()`) for all integer object allocations.

docs/ImmutableList.md

@@ -0,0 +1,37 @@
+# ImmutableList built-in class
+
+`ImmutableList` is an immutable, indexable list value.
+It implements [Array], therefore [Collection] and [Iterable].
+
+Use it when API contracts require a list that cannot be mutated through aliases.
+
+## Creating
+
+    val a = ImmutableList(1,2,3)
+    val b = [1,2,3].toImmutable()
+    val c = (1..3).toImmutableList()
+    >>> void
+
+## Converting
+
+    val i = ImmutableList(1,2,3)
+    val m = i.toMutable()
+    m += 4
+    assertEquals( ImmutableList(1,2,3), i )
+    assertEquals( [1,2,3,4], m )
+    >>> void
+
+## Members
+
+| name          | meaning                                 |
+|---------------|-----------------------------------------|
+| `size`        | number of elements                      |
+| `[index]`     | element access by index                 |
+| `[Range]`     | immutable slice                         |
+| `+`           | append element(s), returns new immutable list |
+| `-`           | remove element(s), returns new immutable list |
+| `toMutable()` | create mutable copy                     |
+
+[Array]: Array.md
+[Collection]: Collection.md
+[Iterable]: Iterable.md

docs/ImmutableMap.md

@@ -0,0 +1,36 @@
+# ImmutableMap built-in class
+
+`ImmutableMap` is an immutable map of key-value pairs.
+It implements [Collection] and [Iterable] of [MapEntry].
+
+## Creating
+
+    val a = ImmutableMap("a" => 1, "b" => 2)
+    val b = Map("a" => 1, "b" => 2).toImmutable()
+    val c = ["a" => 1, "b" => 2].toImmutableMap
+    >>> void
+
+## Converting
+
+    val i = ImmutableMap("a" => 1)
+    val m = i.toMutable()
+    m["a"] = 2
+    assertEquals( 1, i["a"] )
+    assertEquals( 2, m["a"] )
+    >>> void
+
+## Members
+
+| name            | meaning                                  |
+|-----------------|------------------------------------------|
+| `size`          | number of entries                        |
+| `[key]`         | get value by key, or `null` if absent    |
+| `getOrNull(key)`| same as `[key]`                          |
+| `keys`          | list of keys                             |
+| `values`        | list of values                           |
+| `+`             | merge (rightmost wins), returns new immutable map |
+| `toMutable()`   | create mutable copy                      |
+
+[Collection]: Collection.md
+[Iterable]: Iterable.md
+[MapEntry]: Map.md

docs/ImmutableSet.md

@@ -0,0 +1,34 @@
+# ImmutableSet built-in class
+
+`ImmutableSet` is an immutable set of unique elements.
+It implements [Collection] and [Iterable].
+
+## Creating
+
+    val a = ImmutableSet(1,2,3)
+    val b = Set(1,2,3).toImmutable()
+    val c = [1,2,3].toImmutableSet
+    >>> void
+
+## Converting
+
+    val i = ImmutableSet(1,2,3)
+    val m = i.toMutable()
+    m += 4
+    assertEquals( ImmutableSet(1,2,3), i )
+    assertEquals( Set(1,2,3,4), m )
+    >>> void
+
+## Members
+
+| name          | meaning                                             |
+|---------------|-----------------------------------------------------|
+| `size`        | number of elements                                  |
+| `contains(x)` | membership test                                     |
+| `+`, `union`  | union, returns new immutable set                    |
+| `-`, `subtract` | subtraction, returns new immutable set            |
+| `*`, `intersect` | intersection, returns new immutable set         |
+| `toMutable()` | create mutable copy                                 |
+
+[Collection]: Collection.md
+[Iterable]: Iterable.md

docs/Iterable.md

@@ -40,13 +40,13 @@ available, for example
 ## joinToString
 
 This methods convert any iterable to a string joining string representation of each element, optionally transforming it
-and joining using specified suffix.
+and joining using specified separator.
 
-    Iterable.joinToString(suffux=' ', transform=null)
+    Iterable.joinToString(separator=' ', transformer=null)
 
 - if `Iterable` `isEmpty`, the empty string `""` is returned.
-- `suffix` is inserted between items when there are more than one.
-- `transform` of specified is applied to each element, otherwise its `toString()` method is used.
+- `separator` is inserted between items when there are more than one.
+- `transformer` of specified is applied to each element, otherwise its `toString()` method is used.
 
 Here is the sample:
 
@@ -55,7 +55,7 @@ Here is the sample:
     assertEquals( (1..3).joinToString { it * 10 }, "10 20 30")
     >>> void
 
-## `sum` and `sumBy`
+## `sum` and `sumOf`
 
 These, again, does the thing:
 
@@ -68,59 +68,140 @@ These, again, does the thing:
 
     >>> void
 
+## map, filter and their variations
+
+Used to transform or filter the whole iterable stream:
+
+    val source = [1,2,3,4]
+    
+    // map: transform every element to something else
+    assertEquals(["n1", "n2", "n3", "n4"], source.map { "n"+it } )
+    
+    // filter: keep only elements matching the predicate
+    assertEquals([2, 4], source.filter { it % 2 == 0 } )
+
+    // count: count elements matching the predicate
+    assertEquals(2, source.count { it % 2 == 0 } )
+
+    // mapNotNull: transform every element, skipping null results:
+    assertEquals(["n1", "n2", "n4"], source.mapNotNull { if( it == 3 ) null else "n"+it } )
+    
+    // filterNotNull: skip all null elements:
+    assertEquals([1, 2, 4], [1, 2, null, 4].filterNotNull())
+
+    >>> void
+
+You can also use flow variations that return a cold `Flow` instead of a `List`, which is useful for large or infinite sequences:
+
+    val source = [1, 2, 3, 4]
+    
+    // filterFlow: returns a Flow of filtered elements
+    assert( source.filterFlow { it % 2 == 0 } is Flow )
+    
+    // filterFlowNotNull: returns a Flow of non-null elements
+    assert( [1, null, 2].filterFlowNotNull() is Flow )
+    
+    >>> void
+
+## minOf and maxOf
+
+Find the minimum or maximum value of a function applied to each element:
+
+    val source = ["abc", "de", "fghi"]
+    assertEquals(2, source.minOf { (it as String).length })
+    assertEquals(4, source.maxOf { (it as String).length })
+    >>> void
+
+## flatten and flatMap
+
+Work with nested collections:
+
+    val nested = [[1, 2], [3, 4]]
+    
+    // flatten: combine nested collections into one list
+    assertEquals([1, 2, 3, 4], nested.flatten())
+    
+    // flatMap: map each element to a collection and flatten the result
+    assertEquals([1, 10, 2, 20], [1, 2].flatMap { [it, it*10] })
+    
+    >>> void
+
+## findFirst and findFirstOrNull
+
+Search for the first element that satisfies the given predicate:
+
+    val source = [1, 2, 3, 4]
+    assertEquals( 2, source.findFirst { it % 2 == 0 } )
+    assertEquals( 2, source.findFirstOrNull { it % 2 == 0 } )
+    
+    // findFirst throws if not found:
+    assertThrows( NoSuchElementException ) { source.findFirst { it > 10 } }
+    
+    // findFirstOrNull returns null if not found:
+    assertEquals( null, source.findFirstOrNull { it > 10 } )
+    
+    >>> void
+
 ## Instance methods:
 
 | fun/method             | description                                                                     |
 |------------------------|---------------------------------------------------------------------------------|
 | toList()               | create a list from iterable                                                     |
+| toImmutableList()      | create an immutable list from iterable                                          |
 | toSet()                | create a set from iterable                                                      |
+| toImmutableSet         | create an immutable set from iterable                                           |
 | contains(i)            | check that iterable contains `i`                                                |
-| `i in iterator`        | same as `contains(i)`                                                           |
+| `i in iterable`        | same as `contains(i)`                                                           |
 | isEmpty()              | check iterable is empty                                                         |
 | forEach(f)             | call f for each element                                                         |
 | toMap()                | create a map from list of key-value pairs (arrays of 2 items or like)           |
+| toImmutableMap         | create an immutable map from list of key-value pairs                             |
+| any(p)                 | true if any element matches predicate `p`                        |
+| all(p)                 | true if all elements match predicate `p`                         |
 | map(f)                 | create a list of values returned by `f` called for each element of the iterable |
 | indexOf(i)             | return index if the first encounter of i or a negative value if not found       |
 | associateBy(kf)        | create a map where keys are returned by kf that will be called for each element |
+| filter(p)              | create a list of elements matching predicate `p`                |
+| count(p)               | count elements matching predicate `p`                            |
+| filterFlow(p)          | create a [Flow] of elements matching predicate `p`               |
+| filterNotNull()        | create a list of non-null elements                               |
+| filterFlowNotNull()    | create a [Flow] of non-null elements                             |
+| minOf(f)               | return minimum value of `f` applied to elements                  |
+| maxOf(f)               | return maximum value of `f` applied to elements                  |
+| flatten()              | flatten nested collections into a single [List]                  |
+| flatMap(f)             | map each element with `f` and flatten results into a [List]      |
+| findFirst(p)           | return first element matching predicate `p` or throw (1)         |
+| findFirstOrNull(p)     | return first element matching predicate `p` or `null`                            |
 | first                  | first element (1)                                                               |
 | last                   | last element (1)                                                                |
 | take(n)                | return [Iterable] of up to n first elements                                     |
-| taleLast(n)            | return [Iterable] of up to n last elements                                      |
+| takeLast(n)            | return [Iterable] of up to n last elements                                      |
 | drop(n)                | return new [Iterable] without first n elements                                  |
 | dropLast(n)            | return new [Iterable] without last n elements                                   |
 | sum()                  | return sum of the collection applying `+` to its elements (3)                   |
-| sumOf(predicate)       | sum of the modified collection items (3)                                        |
+| sumOf(f)               | sum of the modified collection items (3)                                        |
 | sorted()               | return [List] with collection items sorted naturally                            |
 | sortedWith(comparator) | sort using a comparator that compares elements (1)                              |
 | sortedBy(predicate)    | sort by comparing results of the predicate function                             |
 | joinToString(s,t)      | convert iterable to string, see (2)                                             |
 | reversed()             | create a list containing items from this in reverse order                       |
-| shuffled()             | create a listof shiffled elements                                               |
+| shuffled()             | create a list of shuffled elements                                              |
 
 (1)
-: throws `NoSuchElementException` if there is no such element
+:: throws `NoSuchElementException` if there is no such element
 
 (2)
-: `joinToString(suffix=" ",transform=null)`: suffix is inserted between items if there are more than one, trasnfom is
+:: `joinToString(separator=" ", transformer=null)`: separator is inserted between items if there are more than one, transformer is
 optional function applied to each item that must return result string for an item, otherwise `item.toString()` is used.
 
 (3)
-: sum of empty collection is `null`
-
-    fun Iterable.toList(): List
-    fun Iterable.toSet(): Set
-    fun Iterable.indexOf(element): Int
-    fun Iterable.contains(element): Bool
-    fun Iterable.isEmpty(element): Bool
-    fun Iterable.forEach(block: (Any?)->Void ): Void
-    fun Iterable.map(block: (Any?)->Void ): List
-    fun Iterable.associateBy( keyMaker: (Any?)->Any): Map
+:: sum of empty collection is `null`
 
 ## Abstract methods:
 
     fun iterator(): Iterator
 
-Creates a list by iterating to the end. So, the Iterator should be finite to be used with it.
+For high-performance Kotlin-side interop and custom iterable implementation details, see [Efficient Iterables in Kotlin Interop](EfficientIterables.md).
 
 ## Included in interfaces:
 
@@ -128,14 +209,20 @@ Creates a list by iterating to the end. So, the Iterator should be finite to be
 
 ## Implemented in classes:
 
-- [List], [Range], [Buffer](Buffer.md), [BitBuffer], [Buffer], [Set], [RingBuffer]
+- [List], [ImmutableList], [Range], [Buffer](Buffer.md), [BitBuffer], [Buffer], [Set], [ImmutableSet], [Map], [ImmutableMap], [RingBuffer]
 
 [Collection]: Collection.md
 
 [List]: List.md
+[ImmutableList]: ImmutableList.md
+
+[Flow]: parallelism.md#flow
 
 [Range]: Range.md
 
 [Set]: Set.md
+[ImmutableSet]: ImmutableSet.md
+[Map]: Map.md
+[ImmutableMap]: ImmutableMap.md
 
 [RingBuffer]: RingBuffer.md

docs/Iterator.md

@@ -9,6 +9,9 @@ To implement the iterator you need to implement only two abstract methods:
 
 ### hasNext(): Bool
 
+    // lets test
+    // offset
+
 Should return `true` if call to `next()` will return valid next element.
 
 ### next(): Obj
@@ -20,6 +23,8 @@ must throw `ObjIterationFinishedError`.
 
 Iterators are returned when implementing [Iterable] interface.
 
+For high-performance Kotlin-side interop and custom iterable implementation details, see [Efficient Iterables in Kotlin Interop](EfficientIterables.md).
+
 ## Implemented for classes:
 
 - [List], [Range]

docs/List.md

@@ -1,6 +1,8 @@
 # List built-in class
 
 Mutable list of any objects.
+For immutable list values, see [ImmutableList].
+For observable mutable lists and change hooks, see [ObservableList].
 
 It's class in Lyng is `List`:
 
@@ -92,6 +94,34 @@ Open end ranges remove head and tail elements:
     assert( [1, 2, 3] !== [1, 2, 3])
     >>> void
 
+## Destructuring
+
+Lists can be used as L-values for destructuring assignments. This allows you to unpack list elements into multiple variables.
+
+### Basic Destructuring
+```lyng
+val [a, b, c] = [1, 2, 3]
+```
+
+### With Splats (Variadic)
+A single ellipsis `...` can be used to capture remaining elements into a list. It can be placed at the beginning, middle, or end of the pattern.
+```lyng
+val [head, rest...] = [1, 2, 3] // head=1, rest=[2, 3]
+val [first, middle..., last] = [1, 2, 3, 4, 5] // first=1, middle=[2, 3, 4], last=5
+```
+
+### Nested Patterns
+Destructuring patterns can be nested to unpack multi-dimensional lists.
+```lyng
+val [a, [b, c...], d] = [1, [2, 3, 4], 5]
+```
+
+### Reassignment
+Destructuring can also be used to reassign existing variables:
+```lyng
+[x, y] = [y, x] // Swap values
+```
+
 ## In-place sort
 
 List could be sorted in place, just like [Collection] provide sorted copies, in a very like way:
@@ -130,7 +160,8 @@ List could be sorted in place, just like [Collection] provide sorted copies, in
 | `sort()`                      | in-place sort, natural order                 | void        |
 | `sortBy(predicate)`           | in-place sort bu `predicate` call result (3) | void        |
 | `sortWith(comparator)`        | in-place sort using `comarator` function (4) | void        |
-| `shiffle()`                   | in-place shiffle contents                    |             |
+| `shuffle()`                   | in-place shuffle contents                    |             |
+| `toString()`                 | string representation like `[a,b,c]`         |             |
 
 (1)
 : optimized implementation that override `Array` one
@@ -150,6 +181,50 @@ for `sort()` will be `sort { a, b -> a <=> b }
 
 It inherits from [Iterable] too and thus all iterable methods are applicable to any list.
 
+## Observable list hooks
+
+Observable hooks are provided by module `lyng.observable` and are opt-in:
+
+    import lyng.observable
+
+    val src = [1,2,3]
+    val xs = src.observable()
+    assert(xs is ObservableList<Int>)
+
+    var before = 0
+    var after = 0
+    xs.beforeChange { before++ }
+    xs.onChange { after++ }
+
+    xs += 4
+    xs[0] = 100
+    assertEquals([100,2,3,4], xs)
+    assertEquals(2, before)
+    assertEquals(2, after)
+    >>> void
+
+`beforeChange` runs before mutation commit and may reject it by throwing exception (typically `ChangeRejectionException` from the same module):
+
+    import lyng.observable
+    val xs = [1,2].observable()
+    xs.beforeChange { throw ChangeRejectionException("read only") }
+    assertThrows(ChangeRejectionException) { xs += 3 }
+    assertEquals([1,2], xs)
+    >>> void
+
+`changes()` returns `Flow<ListChange<T>>` of committed events:
+
+    import lyng.observable
+    val xs = [10,20].observable()
+    val it = xs.changes().iterator()
+    xs += 30
+    assert(it.hasNext())
+    val e = it.next()
+    assert(e is ListInsert<Int>)
+    assertEquals([30], (e as ListInsert<Int>).values)
+    it.cancelIteration()
+    >>> void
+
 ## Member inherited from Array
 
 | name             | meaning                        | type  |
@@ -168,3 +243,5 @@ It inherits from [Iterable] too and thus all iterable methods are applicable to
 [Range]: Range.md
 
 [Iterable]: Iterable.md
+[ImmutableList]: ImmutableList.md
+[ObservableList]: ObservableList.md

docs/Map.md

@@ -1,19 +1,23 @@
 # Map
 
-Map is a mutable collection of key-value pars, where keys are unique. Maps could be created with
-constructor or `.toMap` methods. When constructing from a list, each list item must be a [Collection] with exactly 2 elements, for example, a [List].
+Map is a mutable collection of key-value pairs, where keys are unique. You can create maps in two ways:
+- with the constructor `Map(...)` or `.toMap()` helpers; and
+- with map literals using braces: `{ "key": value, id: expr, id: }`.
+For immutable map values, see [ImmutableMap].
+
+When constructing from a list, each list item must be a [Collection] with exactly 2 elements, for example, a [List].
 
 Important thing is that maps can't contain `null`: it is used to return from missing elements.
 
-Constructed map instance is of class `Map` and implements `Collection` (and therefore `Iterable`)
+Constructed map instance is of class `Map` and implements `Collection` (and therefore `Iterable`).
 
-    val map = Map( "foo" => 1, "bar" => "buzz" )
-    assert(map is Map)
-    assert(map.size == 2)
-    assert(map is Iterable)
+    val oldForm = Map( "foo" => 1, "bar" => "buzz" )
+    assert(oldForm is Map)
+    assert(oldForm.size == 2)
+    assert(oldForm is Iterable)
     >>> void
 
-Notice usage of the `=>` operator that creates `MapEntry`, which implements also [Collection] of
+Notice usage of the `=>` operator that creates `MapEntry`, which also implements [Collection] of
 two items, first, at index zero, is a key, second, at index 1, is the value. You can use lists too.
 Map keys could be any objects (hashable, e.g. with reasonable hashCode, most of standard types are). You can access elements with indexing operator:
 
@@ -29,6 +33,36 @@ Map keys could be any objects (hashable, e.g. with reasonable hashCode, most of
     assert( map["foo"] == -1)
     >>> void
 
+## Map literals { ... }
+
+Lyng supports JavaScript-like map literals. Keys can be string literals or identifiers, and there is a handy identifier shorthand:
+
+- String key: `{ "a": 1 }`
+- Identifier key: `{ foo: 2 }` is the same as `{ "foo": 2 }`
+- Identifier shorthand: `{ foo: }` is the same as `{ "foo": foo }`
+
+Access uses brackets: `m["a"]`.
+
+    val x = 10
+    val y = 10
+    val m = { "a": 1, x: x * 2, y: }
+    assertEquals(1, m["a"])      // string-literal key
+    assertEquals(20, m["x"])     // identifier key
+    assertEquals(10, m["y"])     // identifier shorthand expands to y: y
+    >>> void
+
+Trailing commas are allowed for nicer diffs and multiline formatting:
+
+    val m = {
+        "a": 1,
+        b: 2,
+    }
+    assertEquals(1, m["a"]) 
+    assertEquals(2, m["b"]) 
+    >>> void
+
+Empty `{}` is reserved for blocks/lambdas; use `Map()` for an empty map.
+
 To remove item from the collection. use `remove`. It returns last removed item or null. Be careful if you 
 hold nulls in the map - this is not a recommended practice when using `remove` returned value. `clear()` 
 removes all.
@@ -61,7 +95,8 @@ Or iterate its key-value pairs that are instances of [MapEntry] class:
 
     val map = Map( ["foo", 1], ["bar", "buzz"], [42, "answer"] )
     for( entry in map ) {
-        println("map[%s] = %s"(entry.key, entry.value))
+        val e: MapEntry = entry as MapEntry
+        println("map[%s] = %s"(e.key, e.value))
     }
     void
     >>> map[foo] = 1
@@ -110,4 +145,37 @@ is equal.
     assert( m1 != m3 )
     >>> void
 
+## Spreads and merging
+
+Inside map literals you can spread another map with `...` and items will be merged left-to-right; rightmost wins:
+
+    val base = { a: 1, b: 2 }
+    val m = { a: 0, ...base, b: 3, c: 4 }
+    assertEquals(1, m["a"])  // base overwrites a:0
+    assertEquals(3, m["b"])  // literal overwrites spread
+    assertEquals(4, m["c"])  // new key
+    >>> void
+
+Maps and entries can also be merged with `+` and `+=`:
+
+    val m1 = ("x" => 1) + ("y" => 2)
+    assertEquals(1, m1["x"])
+    assertEquals(2, m1["y"])
+
+    val m2 = { "a": 10 } + ("b" => 20)
+    assertEquals(10, m2["a"])
+    assertEquals(20, m2["b"])
+
+    var m3 = { a: 1 }
+    m3 += ("b" => 2)
+    assertEquals(1, m3["a"])
+    assertEquals(2, m3["b"])
+    >>> void
+
+Notes:
+- Map literals always use string keys (identifier keys are converted to strings).
+- Spreads inside map literals and `+`/`+=` merges allow any objects as keys.
+- When you need computed or non-string keys, use the constructor form `Map(...)`, map literals with computed keys (if supported), or build entries with `=>` and then merge.
+
 [Collection](Collection.md)
+[ImmutableMap]: ImmutableMap.md

docs/OOP.md

@@ -1,11 +1,15 @@
-# OO implementation in Lyng
+# Object-oriented programming
 
-## Declaration 
+[//]: # (topMenu)
+
+Lyng supports first class OOP constructs, based on classes with multiple inheritance.
+
+## Class Declaration 
 
 The class clause looks like
 
     class Point(x,y)
-    assert( Point is Class ) 
+    assertEquals("Point", Point.className)
     >>> void
 
 It creates new `Class` with two fields. Here is the more practical sample:
@@ -38,6 +42,271 @@ a _constructor_ that requires two parameters for fields. So when creating it wit
 Form now on `Point` is a class, it's type is `Class`, and we can create instances with it as in the
 example above.
 
+## Singleton Objects
+
+Singleton objects are declared using the `object` keyword. An `object` declaration defines both a class and a single instance of that class at the same time. This is perfect for stateless utilities, global configuration, or shared delegates.
+
+```lyng
+object Config {
+    val version = "1.0.0"
+    val debug = true
+    
+    fun printInfo() {
+        println("App version: " + version)
+    }
+}
+
+// Usage:
+println(Config.version)
+Config.printInfo()
+```
+
+Objects can also inherit from classes or interfaces:
+
+```lyng
+object DefaultLogger : Logger("Default") {
+    override fun log(msg) {
+        println("[DEFAULT] " + msg)
+    }
+}
+```
+
+## Object Expressions
+
+Object expressions allow you to create an instance of an anonymous class. This is useful when you need to provide a one-off implementation of an interface or inherit from a class without declaring a new named subclass.
+
+```lyng
+val worker = object : Runnable {
+    override fun run() {
+        println("Working...")
+    }
+}
+```
+
+Object expressions can implement multiple interfaces and inherit from one class:
+
+```lyng
+val x = object : Base(arg1), Interface1, Interface2 {
+    val property = 42
+    override fun method() = property * 2
+}
+```
+
+### Scoping and `this@object`
+
+Object expressions capture their lexical scope, meaning they can access local variables and members of the outer class. When `this` is rebound (for example, inside an `apply` block), you can use the reserved alias `this@object` to refer to the innermost anonymous object instance.
+
+```lyng
+val handler = object {
+    fun process() {
+        this@object.apply {
+            // here 'this' is rebound to the map/context
+            // but we can still access the anonymous object via this@object
+            println("Processing in " + this@object)
+        }
+    }
+}
+```
+
+### Serialization and Identity
+
+- **Serialization**: Anonymous objects are **not serializable**. Attempting to encode an anonymous object via `Lynon` will throw a `SerializationException`. This is because their class definition is transient and cannot be safely restored in a different session or process.
+- **Type Identity**: Every object expression creates a unique anonymous class. Two identical object expressions will result in two different classes with distinct type identities.
+
+## Nested Declarations
+
+Lyng allows classes, objects, enums, and type aliases to be declared inside another class. These declarations live in the **class namespace** (not the instance), so they do not capture an outer instance and are accessed with a qualifier.
+
+```lyng
+class A {
+    class B(x?)
+    object Inner { val foo = "bar" }
+    type Alias = B
+    enum E { One, Two }
+}
+
+val ab = A.B()
+assertEquals(ab.x, null)
+assertEquals(A.Inner.foo, "bar")
+```
+
+Rules:
+- **Qualified access**: use `Outer.Inner` for nested classes/objects/enums/aliases. Inside `Outer` you can refer to them by unqualified name unless shadowed.
+- **No inner semantics**: nested declarations do not capture an instance of the outer class. They are resolved at compile time.
+- **Visibility**: `private` restricts a nested declaration to the declaring class body (not visible from outside or subclasses).
+- **Reflection name**: a nested class reports `Outer.Inner` (e.g., `A.B::class.name` is `"A.B"`).
+- **Type aliases**: behave as aliases of the qualified nested type and are expanded by the type system.
+
+### Lifted Enum Entries
+
+Enums can optionally lift their entries into the surrounding class namespace using `*`:
+
+```lyng
+class A {
+    enum E* { One, Two }
+}
+
+assertEquals(A.One, A.E.One)
+assertEquals(A.Two, A.E.Two)
+```
+
+Notes:
+- `E*` exposes entries in `A` as if they were direct members (`A.One`).
+- If a name would conflict with an existing class member, compilation fails (no implicit fallback).
+- Without `*`, use the normal `A.E.One` form.
+
+## Properties
+
+Properties allow you to define member accessors that look like fields but execute code when read or written. Unlike regular fields, properties in Lyng do **not** have automatic backing fields; they are pure accessors.
+
+### Basic Syntax
+
+Properties are declared using `val` (read-only) or `var` (read-write) followed by a name and a `get` (and optionally `set`) accessor. Unlike fields, properties do not have automatic storage and must compute their values or delegate to other members.
+
+The standard syntax uses parentheses:
+```lyng
+class Person(private var _age: Int) {
+    // Read-only property
+    val ageCategory 
+        get() {
+            if (_age < 18) "Minor" else "Adult"
+        }
+
+    // Read-write property
+    var age: Int
+        get() { _age }
+        set(value) {
+            if (value >= 0) _age = value
+        }
+}
+```
+
+### Laconic Syntax (Optional Parentheses)
+
+For even cleaner code, you can omit the parentheses for `get` and `set`. This is especially useful for simple expression shorthand:
+
+```lyng
+class Circle(val radius: Real) {
+    // Laconic expression shorthand
+    val area get = π * radius * radius
+    val circumference get = 2 * π * radius
+    
+    fun diameter() = radius * 2
+}
+
+fun median(a, b) = (a + b) / 2
+
+class Counter {
+    private var _count = 0
+    var count get = _count set(v) = _count = v
+}
+```
+
+### Key Rules
+
+- **`val` properties** must have a `get` accessor (with or without parentheses) and cannot have a `set`.
+- **`var` properties** must have both `get` and `set` accessors.
+- **Functions and methods** can use the `=` shorthand to return the result of a single expression.
+- **`override` is mandatory**: If you are overriding a member from a base class, you MUST use the `override` keyword.
+- **No Backing Fields**: There is no magic `field` identifier. If you need to store state, you must declare a separate (usually `private`) field.
+- **Type Inference**: You can omit the type declaration if it can be inferred or if you don't need strict typing.
+
+### Lazy Properties with `cached`
+
+When you want to define a property that is computed only once (on demand) and then remembered, use the built-in `cached` function. This is more efficient than a regular property with `get()` if the computation is expensive, as it avoids re-calculating the value on every access.
+
+```lyng
+class DataService(val id: Int) {
+    // The lambda passed to cached is only executed once, the first time data() is called.
+    val data = cached {
+        println("Fetching data for " + id)
+        // Perform expensive operation
+        "Record " + id
+    }
+}
+
+val service = DataService(42)
+// No printing yet
+println(service.data()) // Prints "Fetching data for 42", then returns "Record 42"
+println(service.data()) // Returns "Record 42" immediately (no second fetch)
+```
+
+Note that `cached` returns a lambda, so you access the value by calling it like a method: `service.data()`. This is a powerful pattern for lazy-loading resources, caching results of database queries, or delaying expensive computations until they are truly needed.
+
+## Delegation
+
+Delegation allows you to hand over the logic of a property or function to another object. This is done using the `by` keyword.
+
+### Property Delegation
+
+Instead of providing `get()` and `set()` accessors, you can delegate them to an object that implements the `getValue` and `setValue` methods.
+
+```lyng
+class User {
+    var name by MyDelegate()
+}
+```
+
+### Function Delegation
+
+You can also delegate a whole function to an object. When the function is called, it will invoke the delegate's `invoke` method.
+
+```lyng
+fun remoteAction by RemoteProxy("actionName")
+```
+
+### The Unified Delegate Interface
+
+A delegate is any object that provides the following methods (all optional depending on usage):
+
+- `getValue(thisRef, name)`: Called when a delegated `val` or `var` is read.
+- `setValue(thisRef, name, newValue)`: Called when a delegated `var` is written.
+- `invoke(thisRef, name, args...)`: Called when a delegated `fun` is invoked.
+- `bind(name, access, thisRef)`: Called once during initialization to configure or validate the delegate.
+
+### Map as a Delegate
+
+Maps can also be used as delegates. When delegated to a property, the map uses the property name as the key:
+
+```lyng
+val settings = { "theme": "dark", "fontSize": 14 }
+val theme by settings
+var fontSize by settings
+
+println(theme)    // "dark"
+fontSize = 16     // Updates settings["fontSize"]
+```
+
+For more details and advanced patterns (like `lazy`, `observable`, and shared stateless delegates), see the [Delegation Guide](delegation.md).
+
+## Instance initialization: init block
+
+In addition to the primary constructor arguments, you can provide an `init` block that runs on each instance creation. This is useful for more complex initializations, side effects, or setting up fields that depend on multiple constructor parameters.
+
+    class Point(val x, val y) {
+       var magnitude
+       
+       init {
+          magnitude = Math.sqrt(x*x + y*y)
+       }
+    }
+
+Key features of `init` blocks:
+- **Scope**: They have full access to `this` members and all primary constructor parameters.
+- **Order**: In a single-inheritance scenario, `init` blocks run immediately after the instance fields are prepared but before the primary constructor body logic.
+- **Multiple blocks**: You can have multiple `init` blocks; they will be executed in the order they appear in the class body.
+
+### Initialization in Multiple Inheritance
+
+In cases of multiple inheritance, `init` blocks are executed following the constructor chaining rule:
+1. All ancestors are initialized first, following the inheritance hierarchy (diamond-safe: each ancestor is initialized exactly once).
+2. The `init` blocks of each class are executed after its parents have been fully initialized.
+3. For a hierarchy `class D : B, C`, the initialization order is: `B`'s chain, then `C`'s chain (skipping common ancestors with `B`), and finally `D`'s own `init` blocks.
+
+### Initialization during Deserialization
+
+When an object is restored from a serialized form (e.g., using `Lynon`), `init` blocks are **re-executed**. This ensures that transient state or derived fields are correctly recalculated upon restoration. However, primary constructors are **not** re-called during deserialization; only the `init` blocks and field initializers are executed to restore the instance state.
+
 Class point has a _method_, or a _member function_ `length()` that uses its _fields_ `x` and `y` to
 calculate the magnitude. Length is called
 
@@ -49,19 +318,68 @@ statements discussed later, there could be default values, ellipsis, etc.
     class Point(x=0,y=0) 
     val p = Point()
     assert( p.x == 0 && p.y == 0 )
+    
+    // Named arguments in constructor calls use colon syntax:
+    val p2 = Point(y: 10, x: 5)
+    assert( p2.x == 5 && p2.y == 10 )
+    
+    // Auto-substitution shorthand for named arguments:
+    val x = 1
+    val y = 2
+    val p3 = Point(x:, y:)
+    assert( p3.x == 1 && p3.y == 2 )
     >>> void
 
+Note that unlike **Kotlin**, which uses `=` for named arguments, Lyng uses `:` to avoid ambiguity with assignment expressions.
+
+### Late-initialized `val` fields
+
+You can declare a `val` field without an immediate initializer if you provide an assignment for it within an `init` block or the class body. This is useful when the initial value depends on logic that cannot be expressed in a single expression.
+
+```lyng
+class DataProcessor(data: Object) {
+    val result: Object
+    
+    init {
+        // Complex initialization logic
+        result = transform(data)
+    }
+}
+```
+
+Key rules for late-init `val`:
+- **Compile-time Check**: The compiler ensures that every `val` declared without an initializer in a class body has at least one assignment within that class body (including `init` blocks). Failing to do so results in a syntax error.
+- **Write-Once**: A `val` can only be assigned once. Even if it was declared without an initializer, once it is assigned a value (e.g., in `init`), any subsequent assignment will throw an `IllegalAssignmentException`.
+- **Access before Initialization**: If you attempt to read a late-init `val` before it has been assigned (for example, by calling a method in `init` that reads the field before its assignment), it will hold a special `Unset` value. Using `Unset` for most operations (like arithmetic or method calls) will throw an `UnsetException`.
+- **No Extensions**: Extension properties do not support late initialization as they do not have per-instance storage. Extension `val`s must always have an initializer or a `get()` accessor.
+
+### The `Unset` singleton
+
+The `Unset` singleton represents a field that has been declared but not yet initialized. While it can be compared and converted to a string, most other operations on it are forbidden to prevent accidental use of uninitialized data.
+
+```lyng
+class T {
+    val x
+    fun check() {
+        if (x == Unset) println("Not ready")
+    }
+    init {
+        check() // Prints "Not ready"
+        x = 42
+    }
+}
+```
+
 ## Methods
 
 Functions defined inside a class body are methods, and unless declared
 `private` are available to be called from outside the class:
 
     class Point(x,y) {
+        // private method:
+        private fun d2() { x*x + y*y }
         // public method declaration:
         fun length() { sqrt(d2()) }
-
-        // private method:
-        private fun d2() {x*x + y*y}
     }
     val p = Point(3,4)
     // private called from inside public: OK
@@ -75,7 +393,7 @@ Functions defined inside a class body are methods, and unless declared
 
 Lyng supports declaring a class with multiple direct base classes. The syntax is:
 
-```
+```lyng
 class Foo(val a) {
     var tag = "F"
     fun runA() { "ResultA:" + a }
@@ -124,16 +442,16 @@ Key rules and features:
 
 - Syntax
   - `class Derived(args) : Base1(b1Args), Base2(b2Args)`
-  - Each direct base may receive constructor arguments specified in the header. Only direct bases receive header args; indirect bases must either be default‑constructible or receive their args through their direct child (future extensions may add more control).
+  - Each direct base may receive constructor arguments specified in the header. Only direct bases receive header args; indirect bases must either be default‑constructible or receive their args through their direct child.
 
-- Resolution order (C3 MRO — active)
+- Resolution order (C3 MRO)
   - Member lookup is deterministic and follows C3 linearization (Python‑like), which provides a monotonic, predictable order for complex hierarchies and diamonds.
   - Intuition: for `class D() : B(), C()` where `B()` and `C()` both derive from `A()`, the C3 order is `D → B → C → A`.
   - The first visible match along this order wins.
 
 - Qualified dispatch
   - Inside a class body, use `this@Type.member(...)` to start lookup at the specified ancestor.
-  - For arbitrary receivers, use casts: `(expr as Type).member(...)` or `(expr as? Type)?.member(...)` (safe‑call `?.` is already available in Lyng).
+  - For arbitrary receivers, use casts: `(expr as Type).member(...)` or `(expr as? Type)?.member(...)`.
   - Qualified access does not relax visibility.
 
 - Field inheritance (`val`/`var`) and collisions
@@ -148,12 +466,215 @@ Key rules and features:
 
 - Visibility
   - `private`: accessible only inside the declaring class body; not visible in subclasses and cannot be accessed via `this@Type` or casts.
-  - `protected`: accessible in the declaring class and in any of its transitive subclasses (including MI), but not from unrelated contexts; qualification/casts do not bypass it.
+  - `protected`: accessible in the declaring class and in any of its transitive subclasses (including MI). Additionally, ancestor classes can access protected members of their descendants if it's an override of a member known to the ancestor. Protected members are not visible from unrelated contexts; qualification/casts do not bypass it.
 
-- Diagnostics
-  - When a member/field is not found, error messages include the receiver class name and the considered linearization order, with suggestions to disambiguate using `this@Type` or casts if appropriate.
-  - Qualifying with a non‑ancestor in `this@Type` reports a clear error mentioning the receiver lineage.
-  - `as`/`as?` cast errors mention the actual and target types.
+## Abstract Classes and Members
+
+An `abstract` class is a class that cannot be instantiated and is intended to be inherited by other classes. It can contain `abstract` members that have no implementation and must be implemented by concrete subclasses.
+
+### Abstract Classes
+
+To declare an abstract class, use the `abstract` modifier:
+
+```lyng
+abstract class Shape {
+    abstract fun area(): Real
+}
+```
+
+Abstract classes can have constructors, fields, and concrete methods, just like regular classes.
+
+### Abstract Members
+
+Methods and variables (`val`/`var`) can be marked as `abstract`. Abstract members must not have a body or initializer.
+
+```lyng
+abstract class Base {
+    abstract fun foo(): Int
+    abstract var bar: String
+}
+```
+
+- **Safety**: `abstract` members cannot be `private`, as they must be visible to subclasses for implementation.
+- **Contract of Capability**: An `abstract val/var` represents a requirement for a capability. It can be implemented by either a **field** (storage) or a **property** (logic) in a subclass.
+
+## Interfaces
+
+An `interface` in Lyng is a synonym for an `abstract class`. Following the principle that Lyng's Multiple Inheritance system is powerful enough to handle stateful contracts, interfaces support everything classes do, including constructors, fields, and `init` blocks.
+
+```lyng
+interface Named(val name: String) {
+    fun greet() { "Hello, " + name }
+}
+
+class Person(name) : Named(name)
+```
+
+Using `interface` instead of `abstract class` is a matter of semantic intent, signaling that the class is primarily intended to be used as a contract in MI.
+
+### Implementation by Parts
+
+One of the most powerful benefits of Lyng's Multiple Inheritance and C3 MRO is the ability to satisfy an interface's requirements "by parts" from different parent classes. Since an `interface` can have state and requirements, a subclass can inherit these requirements and satisfy them using members inherited from other parents in the MRO chain.
+
+Example:
+
+```lyng
+// Interface with state (id) and abstract requirements
+interface Character(val id) {
+    var health
+    var mana
+    
+    fun isAlive() = health > 0
+    fun status() = name + " (#" + id + "): " + health + " HP, " + mana + " MP"
+}
+
+// Parent class 1: provides health
+class HealthPool(var health)
+
+// Parent class 2: provides mana and name
+class ManaPool(var mana) {
+    val name = "Hero"
+}
+
+// Composite class: implements Character by combining HealthPool and ManaPool
+class Warrior(id, h, m) : HealthPool(h), ManaPool(m), Character(id)
+
+val w = Warrior(1, 100, 50)
+assertEquals("Hero (#1): 100 HP, 50 MP", w.status())
+```
+
+In this example, `Warrior` inherits from `HealthPool`, `ManaPool`, and `Character`. The abstract requirements `health` and `mana` from `Character` are automatically satisfied by the matching members inherited from `HealthPool` and `ManaPool`. The `status()` method also successfully finds the `name` field from `ManaPool`. This pattern allows for highly modular and reusable "trait-like" classes that can be combined to fulfill complex contracts without boilerplate proxy methods.
+
+## Overriding and Virtual Dispatch
+
+When a class defines a member that already exists in one of its parents, it is called **overriding**.
+
+### The `override` Keyword
+
+In Lyng, the `override` keyword is **mandatory when declaring a member** that exists in the ancestor chain (MRO).
+
+```lyng
+class Parent {
+    fun foo() = 1
+}
+
+class Child : Parent() {
+    override fun foo() = 2 // Mandatory override keyword
+}
+```
+
+- **Implicit Satisfaction**: If a class inherits an abstract requirement and a matching implementation from different parents, the requirement is satisfied automatically without needing an explicit `override` proxy.
+- **No Accidental Overrides**: If you define a member that happens to match a parent's member but you didn't use `override`, the compiler will throw an error. This prevents the "Fragile Base Class" problem.
+- **Private Members**: Private members in parent classes are NOT part of the virtual interface and cannot be overridden. Defining a member with the same name in a subclass is allowed without `override` and is treated as a new, independent member.
+
+### Visibility Widening
+
+A subclass can increase the visibility of an overridden member (e.g., `protected` → `public`), but it is strictly forbidden from narrowing it (e.g., `public` → `protected`).
+
+### The `closed` Modifier
+
+To prevent a member from being overridden in subclasses, use the `closed` modifier (equivalent to `final` in other languages).
+
+```lyng
+class Critical {
+    closed fun secureStep() { ... }
+}
+```
+
+Attempting to override a `closed` member results in a compile-time error.
+
+## Operator Overloading
+
+Lyng allows you to overload standard operators by defining specific named methods in your classes. When an operator expression is evaluated, Lyng delegates the operation to these methods if they are available.
+
+### Binary Operators
+
+To overload a binary operator, define the corresponding method that takes one argument:
+
+| Operator | Method Name |
+| :--- | :--- |
+| `a + b` | `plus(other)` |
+| `a - b` | `minus(other)` |
+| `a * b` | `mul(other)` |
+| `a / b` | `div(other)` |
+| `a % b` | `mod(other)` |
+| `a && b` | `logicalAnd(other)` |
+| `a \|\| b` | `logicalOr(other)` |
+| `a =~ b` | `operatorMatch(other)` |
+| `a & b` | `bitAnd(other)` |
+| `a \| b` | `bitOr(other)` |
+| `a ^ b` | `bitXor(other)` |
+| `a << b` | `shl(other)` |
+| `a >> b` | `shr(other)` |
+
+Example:
+```lyng
+class Vector(val x, val y) {
+    fun plus(other) = Vector(x + other.x, y + other.y)
+    override fun toString() = "Vector(${x}, ${y})"
+}
+
+val v1 = Vector(1, 2)
+val v2 = Vector(3, 4)
+assertEquals(Vector(4, 6), v1 + v2)
+```
+
+### Unary Operators
+
+Unary operators are overloaded by defining methods with no arguments:
+
+| Operator | Method Name |
+| :--- | :--- |
+| `-a` | `negate()` |
+| `!a` | `logicalNot()` |
+| `~a` | `bitNot()` |
+
+### Assignment Operators
+
+Assignment operators like `+=` first attempt to call a specific assignment method. If that method is not defined, they fall back to a combination of the binary operator and a regular assignment (e.g., `a = a + b`).
+
+| Operator | Method Name | Fallback |
+| :--- | :--- | :--- |
+| `a += b` | `plusAssign(other)` | `a = a + b` |
+| `a -= b` | `minusAssign(other)` | `a = a - b` |
+| `a *= b` | `mulAssign(other)` | `a = a * b` |
+| `a /= b` | `divAssign(other)` | `a = a / b` |
+| `a %= b` | `modAssign(other)` | `a = a % b` |
+
+Example of in-place mutation:
+```lyng
+class Counter(var value) {
+    fun plusAssign(n) {
+        value = value + n
+    }
+}
+
+val c = Counter(10)
+c += 5
+assertEquals(15, c.value)
+```
+
+### Comparison Operators
+
+Comparison operators use `compareTo` and `equals`.
+
+| Operator | Method Name |
+| :--- | :--- |
+| `a == b`, `a != b` | `equals(other)` |
+| `<`, `>`, `<=`, `>=`, `<=>` | `compareTo(other)` |
+
+- `compareTo` should return:
+  - `0` if `a == b`
+  - A negative integer if `a < b`
+  - A positive integer if `a > b`
+- The `<=>` (shuttle) operator returns the result of `compareTo` directly.
+- `equals` returns a `Bool`. If `equals` is not explicitly defined, Lyng falls back to `compareTo(other) == 0`.
+
+> **Note**: Methods that are already defined in the base `Obj` class (like `equals`, `toString`, or `contains`) require the `override` keyword when redefined in your class or as an extension. Other operator methods (like `plus` or `negate`) do not require `override` unless they are already present in your class's hierarchy.
+
+### Increment and Decrement
+
+`++` and `--` operators are implemented using `plus(1)` or `minus(1)` combined with an assignment back to the variable. If the variable is a field or local variable, it will be updated with the result of the operation.
 
 Compatibility notes:
 
@@ -164,6 +685,97 @@ Compatibility notes:
 
 Earlier drafts and docs described a declaration‑order depth‑first linearization. Lyng now uses C3 MRO for member lookup and disambiguation. Most code should continue to work unchanged, but in rare edge cases involving diamonds or complex multiple inheritance, the chosen base for an ambiguous member may change to reflect C3. If needed, disambiguate explicitly using `this@Type.member(...)` inside class bodies or casts `(expr as Type).member(...)` from outside.
 
+## Enums
+
+Lyng provides lightweight enums for representing a fixed set of named constants. Enums are classes whose instances are predefined and singletons.
+
+Current syntax supports simple enum declarations with just entry names:
+
+    enum Color {
+        RED, GREEN, BLUE
+    }
+
+Usage:
+
+- Type of entries: every entry is an instance of its enum type.
+
+      assert( Color.RED is Color )
+
+- Order and names: each entry has zero‑based `ordinal` and string `name`.
+
+      assertEquals(0, Color.RED.ordinal)
+      assertEquals("BLUE", Color.BLUE.name)
+
+- All entries as a list in declaration order: `EnumType.entries`.
+
+      assertEquals([Color.RED, Color.GREEN, Color.BLUE], Color.entries)
+
+- Lookup by name: `EnumType.valueOf("NAME")` → entry.
+
+      assertEquals(Color.GREEN, Color.valueOf("GREEN"))
+
+- Equality and comparison:
+  - Equality uses identity of entries, e.g., `Color.RED == Color.valueOf("RED")`.
+  - Cross‑enum comparisons are not allowed.
+  - Ordering comparisons use `ordinal`.
+
+      assert( Color.RED == Color.valueOf("RED") )
+      assert( Color.RED.ordinal < Color.BLUE.ordinal )
+      >>> void
+
+### Enums with `when`
+
+Use `when(subject)` with equality branches for enums. See full `when` guide: [The `when` statement](when.md).
+
+    enum Color { RED, GREEN, BLUE }
+
+    fun describe(c) {
+        when(c) {
+            Color.RED, Color.GREEN -> "primary-like"
+            Color.BLUE -> "blue"
+            else -> "unknown"   // if you pass something that is not a Color
+        }
+    }
+    assertEquals("primary-like", describe(Color.RED))
+    assertEquals("blue", describe(Color.BLUE))
+    >>> void
+
+### Serialization
+
+Enums are serialized compactly with Lynon: the encoded value stores just the entry ordinal within the enum type, which is both space‑efficient and fast.
+
+    import lyng.serialization
+
+    enum Color { RED, GREEN, BLUE }
+
+    val e = Lynon.encode(Color.BLUE)
+    val decoded = Lynon.decode(e)
+    assertEquals(Color.BLUE, decoded)
+    >>> void
+
+Notes and limitations (current version):
+
+- Enum declarations support only simple entry lists: no per‑entry bodies, no custom constructors, and no user‑defined methods/fields on the enum itself yet.
+- `name` and `ordinal` are read‑only properties of an entry.
+- `entries` is a read‑only list owned by the enum type.
+
+## Exception Classes
+
+You can define your own exception classes by inheriting from the built-in `Exception` class. User-defined exceptions are regular classes and can have their own properties and methods.
+
+```lyng
+class MyError(val code, m) : Exception(m)
+
+try {
+    throw MyError(500, "Internal Server Error")
+}
+catch(e: MyError) {
+    println("Error " + e.code + ": " + e.message)
+}
+```
+
+For more details on error handling, see the [Exceptions Handling Guide](exceptions_handling.md).
+
 ## fields and visibility
 
 It is possible to add non-constructor fields:
@@ -196,6 +808,69 @@ Are declared with var
     assert( p.isSpecial == true )
     >>> void
 
+### Restricted Setter Visibility
+
+You can restrict the visibility of a `var` field's or property's setter by using `private set` or `protected set` modifiers. This allows the member to be publicly readable but only writable from within the class or its subclasses.
+
+#### On Fields
+
+```lyng
+class SecretCounter {
+    var count = 0
+        private set // Can be read anywhere, but written only in SecretCounter
+        
+    fun increment() { count++ }
+}
+
+val c = SecretCounter()
+println(c.count) // OK
+c.count = 10     // Throws IllegalAccessException
+c.increment()    // OK
+```
+
+#### On Properties
+
+You can also apply restricted visibility to custom property setters:
+
+```lyng
+class Person(private var _age: Int) {
+    var age
+        get() = _age
+        private set(v) { if (v >= 0) _age = v }
+}
+```
+
+#### Protected Setters and Inheritance
+
+A `protected set` allows subclasses to modify a field that is otherwise read-only to the public:
+
+```lyng
+class Base {
+    var state = "initial"
+        protected set
+}
+
+class Derived : Base() {
+    fun changeState(newVal) {
+        state = newVal // OK: protected access from subclass
+    }
+}
+
+val d = Derived()
+println(d.state) // OK: "initial"
+d.changeState("updated")
+println(d.state) // OK: "updated"
+d.state = "bad"  // Throws IllegalAccessException: public write not allowed
+```
+
+### Key Rules and Limitations
+
+- **Only for `var`**: Restricted setter visibility cannot be used with `val` declarations, as they are inherently read-only. Attempting to use it with `val` results in a syntax error.
+- **Class Body Only**: These modifiers can only be used on members declared within the class body. They are not supported for primary constructor parameters.
+- **`private set`**: The setter is only accessible within the same class context (specifically, when `this` is an instance of that class).
+- **`protected set`**: The setter is accessible within the declaring class and all its transitive subclasses.
+- **Multiple Inheritance**: In MI scenarios, visibility is checked against the class that actually declared the member. Qualified access (e.g., `this@Base.field = value`) also respects restricted setter visibility.
+
 ### Private fields
 
 Private fields are visible only _inside the class instance_:
@@ -223,23 +898,44 @@ Private fields are visible only _inside the class instance_:
     void
     >>> void
 
+### Transient fields
+
+You can mark a field or a constructor parameter as transient using the `@Transient` attribute. Transient members are ignored during serialization (Lynon and JSON) and are also excluded from structural equality (`==`) checks.
+
+```lyng
+class Session(@Transient val token, val userId) {
+    @Transient var lastAccess = time.now()
+    var data = Map()
+}
+```
+
+For more details on how transient fields behave during restoration, see the [Serialization Guide](serialization.md).
+
 ### Protected members
 
-Protected members are available to the declaring class and all of its transitive subclasses (including via MI), but not from unrelated contexts:
+Protected members are available to the declaring class and all of its transitive subclasses (including via MI). Additionally, an ancestor class can access a `protected` member of its descendant if the ancestor also defines or inherits a member with the same name (i.e., it is an override of something the ancestor knows about). 
 
-```
-class A() {
-    protected fun ping() { "pong" }
-}
-class B() : A() {
-    fun call() { this@A.ping() }
+Protected members are not available from unrelated contexts:
+
+```lyng
+class Base {
+    abstract protected fun foo()
+    
+    fun bar() {
+        // Ancestor can see foo() because it's an override 
+        // of a member it defines (even as abstract):
+        foo()
+    }
 }
 
-val b = B()
-assertEquals("pong", b.call())
+class Derived : Base {
+    override protected fun foo() { "ok" }
+}
+
+assertEquals("ok", Derived().bar())
 
 // Unrelated access is forbidden, even via cast
-assertThrows { (b as A).ping() }
+assertThrows { (Derived() as Base).foo() }
 ```
 
 It is possible to provide private constructor parameters so they can be
@@ -282,7 +978,7 @@ You can mark a field or a method as static. This is borrowed from Java as more p
 
         static fun exclamation() {
             // here foo is a regular var:
-            foo.x + "!"
+        Value.foo.x + "!"
         }
     }
     assertEquals( Value.foo.x, "foo" )
@@ -293,47 +989,29 @@ You can mark a field or a method as static. This is borrowed from Java as more p
     assertEquals( "bar!", Value.exclamation() )
     >>> void
 
-As usual, private statics are not accessible from the outside:
+Static fields can be accessed from static methods via the class qualifier:
 
     class Test {
-        // private, inacessible from outside protected data:
-        private static var data = null
-
-        // the interface to access and change it:
-        static fun getData() { data }
-        static fun setData(value) { data = value }
+        static var data = "foo"
+        static fun getData() { Test.data }
     }
 
-    // no direct access:
-    assertThrows { Test.data }
-
-    // accessible with the interface:
-    assertEquals( null, Test.getData() )
-    Test.setData("fubar")
-    assertEquals("fubar", Test.getData() )
+    assertEquals( "foo", Test.getData() )
+    Test.data = "bar"
+    assertEquals("bar", Test.getData() )
     >>> void
 
 # Extending classes
 
-It sometimes happen that the class is missing some particular functionality that can be _added to it_ without rewriting its inner logic and using its private state. In this case _extension methods_ could be used, for example. we want to create an extension method
-that would test if some object of unknown type contains something that can be interpreted
-as an integer. In this case we _extend_ class `Object`, as it is the parent class for any instance of any type:
+It sometimes happen that the class is missing some particular functionality that can be _added to it_ without rewriting its inner logic and using its private state. In this case _extension members_ could be used.
 
-        fun Object.isInteger() {
-            when(this) {
-                // already Int?
-                is Int -> true
+## Extension methods
 
-                // real, but with no declimal part?
-                is Real -> toInt() == this
+For example, we want to create an extension method that would test if a value can be interpreted as an integer:
 
-                // string with int or real reuusig code above
-                is String -> toReal().isInteger()
-                
-                // otherwise, no:
-                else -> false
-            }
-        }
+        fun Int.isInteger() { true }
+        fun Real.isInteger() { this.toInt() == this }
+        fun String.isInteger() { (this.toReal() as Real).isInteger() }
 
         // Let's test:
         assert( 12.isInteger() == true )
@@ -342,10 +1020,67 @@ as an integer. In this case we _extend_ class `Object`, as it is the parent clas
         assert( ! "5.2".isInteger() )
         >>> void
 
-__Important note__ as for version 0.6.9, extensions are in __global scope__. It means, that once applied to a global type (Int in our sample), they will be available for _all_ contexts, even new created, 
-as they are modifying the type, not the context.
+## Extension properties
 
-Beware of it. We might need to reconsider it later.
+Just like methods, you can extend existing classes with properties. These can be defined using simple initialization (for `val` only) or with custom accessors.
+
+### Simple val extension
+
+A read-only extension can be defined by assigning an expression:
+
+```lyng
+val String.isLong = length > 10
+
+val s = "Hello, world!"
+assert(s.isLong)
+```
+
+### Properties with accessors
+
+For more complex logic, use `get()` and `set()` blocks:
+
+```lyng
+class Box(var value: Int)
+
+var Box.doubledValue
+    get() = value * 2
+    set(v) = value = v / 2
+
+val b = Box(10)
+assertEquals(20, b.doubledValue)
+b.doubledValue = 30
+assertEquals(15, b.value)
+```
+
+Extension members are strictly barred from accessing private members of the class they extend, maintaining encapsulation.
+
+### Extension Scoping and Isolation
+
+Extensions in Lyng are **scope-isolated**. This means an extension is only visible within the scope where it is defined and its child scopes. This reduces the "attack surface" and prevents extensions from polluting the global space or other modules.
+
+#### Scope Isolation Example
+
+You can define different extensions with the same name in different scopes:
+
+```lyng
+fun scopeA() {
+    val Int.description = "Number: " + toString()
+    assertEquals("Number: 42", 42.description)
+}
+
+fun scopeB() {
+    val Int.description = "Value: " + toString()
+    assertEquals("Value: 42", 42.description)
+}
+
+scopeA()
+scopeB()
+
+// Outside those scopes, Int.description is not defined
+assertThrows { 42.description }
+```
+
+This isolation ensures that libraries can use extensions internally without worrying about name collisions with other libraries or the user's code. When a module is imported using `use`, its top-level extensions become available in the importing scope.
 
 ## dynamic symbols
 
@@ -380,7 +1115,7 @@ The same we can provide writable dynamic fields (var-type), adding set method:
                 // mutable field
                 "bar" -> storedValueForBar 
 
-                else -> throw SymbolNotFoundException()
+                else -> throw SymbolNotFound()
             }
         }
         set { name, value ->
@@ -464,12 +1199,12 @@ request](https://gitea.sergeych.net/SergeychWorks/lyng/issues).
 - ObjClass sole parent is Obj
 - ObjClass contains code for instance methods, class fields, hierarchy information.
 - Class information is also scoped. 
-- We acoid imported classes duplication using packages and import caching, so the same imported module is the same object in all its classes.
+- We avoid imported classes duplication using packages and import caching, so the same imported module is the same object in all its classes.
 
 ## Instances
 
 Result of executing of any expression or statement in the Lyng is the object that
-inherits `Obj`, but is not `Obj`. For example it could be Int, void, null, real, string, bool, etc.
+inherits `Obj`, but is not `Obj`. For example, it could be Int, void, null, real, string, bool, etc.
 
 This means whatever expression returns or the variable holds, is the first-class
 object, no differenes. For example:
@@ -526,3 +1261,8 @@ Regular methods are called on instances as usual `instance.method()`. The method
 TBD
 
 [argument list](declaring_arguments.md)
+### Visibility from within closures and instance scopes
+
+When a closure executes within a method, the closure retains the lexical class context of its creation site. This means private/protected members of that class remain accessible where expected (subject to usual visibility rules). Field resolution checks the declaring class and validates access using the preserved `currentClassCtx`.
+
+See also: [Scopes and Closures: resolution and safety](scopes_and_closures.md)

docs/ObservableList.md

@@ -0,0 +1,70 @@
+# ObservableList module
+
+`ObservableList` lives in explicit module `lyng.observable`.
+
+Import it first:
+
+    import lyng.observable
+    >>> void
+
+Create from a regular mutable list:
+
+    import lyng.observable
+    val xs = [1,2,3].observable()
+    assert(xs is ObservableList<Int>)
+    assertEquals([1,2,3], xs)
+    >>> void
+
+## Hook flow
+
+Event order is:
+1. `beforeChange(change)` listeners
+2. mutation commit
+3. `onChange(change)` listeners
+4. `changes()` flow emission
+
+Rejection is done by throwing in `beforeChange`.
+
+    import lyng.observable
+    val xs = [1,2].observable()
+    xs.beforeChange {
+        throw ChangeRejectionException("no mutation")
+    }
+    assertThrows(ChangeRejectionException) { xs += 3 }
+    assertEquals([1,2], xs)
+    >>> void
+
+## Subscriptions
+
+`beforeChange` and `onChange` return `Subscription`.
+Call `cancel()` to unsubscribe.
+
+    import lyng.observable
+    val xs = [1].observable()
+    var hits = 0
+    val sub = xs.onChange { hits++ }
+    xs += 2
+    sub.cancel()
+    xs += 3
+    assertEquals(1, hits)
+    >>> void
+
+## Change events
+
+`changes()` returns `Flow<ListChange<T>>` with concrete event classes:
+- `ListInsert`
+- `ListSet`
+- `ListRemove`
+- `ListClear`
+- `ListReorder`
+
+    import lyng.observable
+    val xs = [10,20].observable()
+    val it = xs.changes().iterator()
+    xs[1] = 200
+    val ev = it.next()
+    assert(ev is ListSet<Int>)
+    assertEquals(20, (ev as ListSet<Int>).oldValue)
+    assertEquals(200, ev.newValue)
+    it.cancelIteration()
+    >>> void

docs/Range.md

@@ -45,10 +45,11 @@ are equal or within another, taking into account the end-inclusiveness:
     assert( (1..<3) in (1..3) )
     >>> void
 
-## Finite Ranges are iterable
+## Ranges are iterable
 
-So given a range with both ends, you can assume it is [Iterable]. This automatically let
-use finite ranges in loops and convert it to lists:
+Finite ranges are [Iterable] and can be used in loops and list conversions.
+Open-ended ranges are iterable only with an explicit `step`, and open-start
+ranges are never iterable.
 
     assert( [-2, -1, 0, 1] == (-2..1).toList() )
     >>> void
@@ -62,6 +63,8 @@ In spite of this you can use ranges in for loops:
     >>> 3
     >>> void
 
+The loop variable is read-only inside the loop body (behaves like a `val`).
+
 but
 
     for( i in 1..<3 ) 
@@ -70,6 +73,26 @@ but
     >>> 2
     >>> void
 
+### Stepped ranges
+
+Use `step` to change the iteration increment. The range bounds still define membership,
+so iteration ends when the next value is no longer in the range.
+
+    assert( [1,3,5] == (1..5 step 2).toList() )
+    assert( [1,3] == (1..<5 step 2).toList() )
+    assert( ['a','c','e'] == ('a'..'e' step 2).toList() )
+    >>> void
+
+Real ranges require an explicit step:
+
+    assert( [0,0.25,0.5,0.75,1.0] == (0.0..1.0 step 0.25).toList() )
+    >>> void
+
+Open-ended ranges require an explicit step to iterate:
+
+    (0.. step 1).take(3).toList()
+    >>> [0,1,2]
+
 ## Character ranges
 
 You can use Char as both ends of the closed range:
@@ -98,10 +121,12 @@ Exclusive end char ranges are supported too:
 | isEndInclusive  | true for '..'                | Bool          |
 | isOpen          | at any end                   | Bool          |
 | isIntRange      | both start and end are Int   | Bool          |
-| start           |                              | Bool          |
-| end             |                              | Bool          |
+| step            | explicit iteration step      | Any?          |
+| start           |                              | Any?          |
+| end             |                              | Any?          |
 | size            | for finite ranges, see above | Long          |
 | []              | see above                    |               |
-|                 |                              |               |
+
+Ranges are also used with the `clamp(value, range)` function and the `value.clamp(range)` extension method to limit values within boundaries.
 
 [Iterable]: Iterable.md

docs/Real.md

@@ -19,6 +19,7 @@ you can use it's class to ensure type:
 |-----------------|-------------------------------------------------------------|------|
 | `.roundToInt()` | round to nearest int like round(x)                          | Int  |
 | `.toInt()`      | convert integer part of real to `Int` dropping decimal part | Int  |
+| `.clamp(range)` | clamp value within range boundaries                         | Real |
 |                 |                                                             |      |
 |                 |                                                             |      |
 |                 |                                                             |      |

docs/Regex.md

@@ -24,13 +24,14 @@ counterpart, _not match_ operator `!~`:
 
 When you need to find groups, and more detailed match information, use `Regex.find`:
 
-    val result = Regex("abc(\d)(\d)(\d)").find( "bad456 good abc123")
+    val result: RegexMatch? = Regex("abc(\d)(\d)(\d)").find( "bad456 good abc123")
     assert( result  != null )
-    assertEquals( 12 .. 17, result.range )
-    assertEquals( "abc123", result[0] )
-    assertEquals( "1", result[1] )
-    assertEquals( "2", result[2] )
-    assertEquals( "3", result[3] )
+    val match: RegexMatch = result as RegexMatch
+    assertEquals( 12 ..< 17, match.range )
+    assertEquals( "abc123", match[0] )
+    assertEquals( "1", match[1] )
+    assertEquals( "2", match[2] )
+    assertEquals( "3", match[3] )
     >>> void
 
 Note that the object `RegexMatch`, returned by [Regex.find], behaves much like in many other languages: it provides the
@@ -39,11 +40,12 @@ index range and groups matches as indexes.
 Match operator actually also provides `RegexMatch` in `$~` reserved variable (borrowed from Ruby too):
 
     assert( "bad456 good abc123" =~ "abc(\d)(\d)(\d)".re )
-    assertEquals( 12 .. 17, $~.range )
-    assertEquals( "abc123", $~[0] )
-    assertEquals( "1", $~[1] )
-    assertEquals( "2", $~[2] )
-    assertEquals( "3", $~[3] )
+    val match2: RegexMatch = $~ as RegexMatch
+    assertEquals( 12 ..< 17, match2.range )
+    assertEquals( "abc123", match2[0] )
+    assertEquals( "1", match2[1] )
+    assertEquals( "2", match2[2] )
+    assertEquals( "3", match2[3] )
     >>> void
 
 This is often more readable than calling `find`.
@@ -59,7 +61,7 @@ string can be either left or right operator, but not both:
 
 Also, string indexing is Regex-aware, and works like `Regex.find` (_not findall!_):
 
-    assert( "cd" == "abcdef"[ "c.".re ].value )
+    assert( "cd" == ("abcdef"[ "c.".re ] as RegexMatch).value )
     >>> void
 
 
@@ -88,4 +90,3 @@ Also, string indexing is Regex-aware, and works like `Regex.find` (_not findall!
 [List]: List.md
 
 [Range]: Range.md
-

docs/Set.md

@@ -1,7 +1,8 @@
-# List built-in class
+# Set built-in class
 
 Mutable set of any objects: a group of different objects, no repetitions.
 Sets are not ordered, order of appearance does not matter.
+For immutable set values, see [ImmutableSet].
 
     val set = Set(1,2,3, "foo")
     assert( 1 in set )
@@ -26,8 +27,8 @@ no indexing. Use [set.toList] as needed.
 
     // intersection
     assertEquals( Set(1,4), Set(3, 1, 4).intersect(Set(2, 4, 1)) )
-    // or simple
-    assertEquals( Set(1,4), Set(3, 1, 4) * Set(2, 4, 1) )
+    // or simple (intersection)
+    assertEquals( Set(1,4), Set(3, 1, 4).intersect(Set(2, 4, 1)) )
 
     // To find collection elements not present in another collection, use the 
     // subtract() or `-`:
@@ -92,3 +93,4 @@ Also, it inherits methods from [Iterable].
 
 
 [Range]: Range.md
+[ImmutableSet]: ImmutableSet.md

docs/Testing.md

@@ -0,0 +1,121 @@
+# Testing and Assertions
+
+Lyng provides several built-in functions for testing and verifying code behavior. These are available in all scripts.
+
+## Basic Assertions
+
+### `assert`
+
+Assert that a condition is true.
+
+    assert(condition, message=null)
+
+- `condition`: A boolean expression.
+- `message` (optional): A string message to include in the exception if the assertion fails.
+
+If the condition is false, it throws an `AssertionFailedException`.
+
+```lyng
+assert(1 + 1 == 2)
+assert(true, "This should be true")
+```
+
+### `assertEquals` and `assertEqual`
+
+Assert that two values are equal. `assertEqual` is an alias for `assertEquals`.
+
+    assertEquals(expected, actual)
+    assertEqual(expected, actual)
+
+If `expected != actual`, it throws an `AssertionFailedException` with a message showing both values.
+
+```lyng
+assertEquals(4, 2 * 2)
+assertEqual("hello", "hel" + "lo")
+```
+
+### `assertNotEquals`
+
+Assert that two values are not equal.
+
+    assertNotEquals(unexpected, actual)
+
+If `unexpected == actual`, it throws an `AssertionFailedException`.
+
+```lyng
+assertNotEquals(5, 2 * 2)
+```
+
+## Exception Testing
+
+### `assertThrows`
+
+Assert that a block of code throws an exception.
+
+    assertThrows(code)
+    assertThrows(expectedExceptionClass, code)
+
+- `expectedExceptionClass` (optional): The class of the exception that is expected to be thrown.
+- `code`: A lambda block or statement to execute.
+
+If the code does not throw an exception, an `AssertionFailedException` is raised. 
+If an `expectedExceptionClass` is provided, the thrown exception must be of that class (or its subclass), otherwise an error is raised.
+
+`assertThrows` returns the caught exception object if successful.
+
+```lyng
+// Just assert that something is thrown
+assertThrows { 1 / 0 }
+
+// Assert that a specific exception class is thrown
+assertThrows(NoSuchElementException) { 
+    [1, 2, 3].findFirst { it > 10 } 
+}
+
+// You can use the returned exception
+val ex = assertThrows { throw Exception("custom error") }
+assertEquals("custom error", ex.message)
+```
+
+## Other Validation Functions
+
+While not strictly for testing, these functions help in defensive programming:
+
+### `require`
+
+    require(condition, message="requirement not met")
+
+Throws an `IllegalArgumentException` if the condition is false. Use this for validating function arguments.
+
+If we want to evaluate the message lazily:
+
+    require(condition) { "requirement not met: %s"(someData) }
+
+In this case, formatting will only occur if the condition is not met.
+
+### `check`
+
+    check(condition, message="check failed")
+
+Throws an `IllegalStateException` if the condition is false. Use this for validating internal state.
+
+With lazy message evaluation:
+
+    check(condition) { "check failed: %s"(someData) }
+
+In this case, formatting will only occur if the condition is not met.
+
+### TODO
+
+It is easy to mark some code and make it throw a special exception at cone with:
+
+    TODO()
+
+or
+
+    TODO("some message")
+
+It raises an `NotImplementedException` with the given message. You can catch it
+as any other exception when necessary.
+
+Many IDE and editors have built-in support for marking code with TODOs.

docs/advanced_topics.md

@@ -105,6 +105,7 @@ arguments list in almost arbitrary ways. For example:
         var result = ""
         for( a in args ) result += a
     }
+    // loop variables are read-only inside the loop body
 
     assertEquals( 
         "4231", 
@@ -153,8 +154,15 @@ Function annotation can have more args specified at call time. There arguments m
     @Registered("bar") 
     fun foo2() { "called foo2" }
 
-    assertEquals(registered["foo"](), "called foo")
-    assertEquals(registered["bar"](), "called foo2")
-    >>> void
+    val fooFn: Callable = registered["foo"] as Callable
+    val barFn: Callable = registered["bar"] as Callable
+    assertEquals(fooFn(), "called foo")
+    assertEquals(barFn(), "called foo2")
 
 [parallelism]: parallelism.md
+
+## Scopes and Closures: resolution and safety
+
+Closures and dynamic scope graphs require care to avoid accidental recursion and to keep name resolution predictable. See the dedicated page for detailed rules, helper APIs, and best practices:
+
+- Scopes and Closures: resolution and safety → [scopes_and_closures.md](scopes_and_closures.md)

docs/ai_language_reference.md

@@ -0,0 +1,219 @@
+# Lyng Language Reference for AI Agents (Current Compiler State)
+
+Purpose: dense, implementation-first reference for generating valid Lyng code.
+
+Primary sources used: `lynglib/src/commonMain/kotlin/net/sergeych/lyng/{Parser,Token,Compiler,Script,TypeDecl}.kt`, `lynglib/stdlib/lyng/root.lyng`, tests in `lynglib/src/commonTest` and `lynglib/src/jvmTest`.
+
+## 1. Ground Rules
+- Resolution is compile-time-first. Avoid runtime name/member lookup assumptions.
+- `lyng.stdlib` is auto-seeded for normal scripts (default import manager).
+- Use explicit casts when receiver type is unknown (`Object`/`Obj`).
+- Prefer modern null-safe operators (`?.`, `?:`/`??`, `?=`, `as?`, `!!`).
+- Do not rely on fallback opcodes or dynamic member fallback semantics.
+
+## 2. Lexical Syntax
+- Comments: `// line`, `/* block */`.
+- Strings: `"..."` (supports escapes). Multiline string content is normalized by indentation logic.
+  - Supported escapes: `\n`, `\r`, `\t`, `\"`, `\\`, `\uXXXX` (4 hex digits).
+  - Unicode escapes use exactly 4 hex digits (for example: `"\u0416"` -> `Ж`).
+  - Unknown `\x` escapes in strings are preserved literally as two characters (`\` and `x`).
+- Numbers: `Int` (`123`, `1_000`), `Real` (`1.2`, `1e3`), hex (`0xFF`).
+- Char: `'a'`, escaped chars supported.
+  - Supported escapes: `\n`, `\r`, `\t`, `\'`, `\\`, `\uXXXX` (4 hex digits).
+  - Backslash character in a char literal must be written as `'\\'` (forms like `'\'` are invalid).
+- Labels:
+  - statement label: `loop@ for (...) { ... }`
+  - label reference: `break@loop`, `continue@loop`, `return@fnLabel`
+- Keywords/tokens include (contextual in many places):
+  - declarations: `fun`/`fn`, `val`, `var`, `class`, `object`, `interface`, `enum`, `type`, `init`
+  - modifiers: `private`, `protected`, `static`, `abstract`, `closed`, `override`, `extern`, `open`
+  - flow: `if`, `else`, `when`, `for`, `while`, `do`, `try`, `catch`, `finally`, `throw`, `return`, `break`, `continue`
+
+## 3. Literals and Core Expressions
+- Scalars: `null`, `true`, `false`, `void`.
+- List literal: `[a, b, c]`, spreads with `...`.
+  - Spread positions: beginning, middle, end are all valid: `[...a]`, `[0, ...a, 4]`, `[head, ...mid, tail]`.
+  - Spread source must be a `List` at runtime (non-list spread raises an error).
+- Map literal: `{ key: value, x:, ...otherMap }`.
+  - `x:` means shorthand `x: x`.
+  - Map spread source must be a `Map`.
+- Range literals:
+  - inclusive: `a..b`
+  - exclusive end: `a..<b`
+  - open-ended forms are supported (`a..`, `..b`, `..`).
+  - optional step: `a..b step 2`
+- Lambda literal:
+  - with params: `{ x, y -> x + y }`
+  - implicit `it`: `{ it + 1 }`
+- Ternary conditional is supported: `cond ? thenExpr : elseExpr`.
+
+## 3.1 Splats in Calls and Lambdas
+- Declaration-side variadic parameters use ellipsis suffix:
+  - functions: `fun f(head, tail...) { ... }`
+  - lambdas: `{ x, rest... -> ... }`
+- Call-side splats use `...expr` and are expanded by argument kind:
+  - positional splat: `f(...[1,2,3])`
+  - named splat: `f(...{ a: 1, b: 2 })` (map-style)
+- Runtime acceptance for splats:
+  - positional splat accepts `List` and general `Iterable` (iterable is converted to list first).
+  - named splat accepts `Map` with string keys only.
+- Ordering/validation rules (enforced):
+  - positional argument cannot follow named arguments (except trailing-block parsing case).
+  - positional splat cannot follow named arguments.
+  - duplicate named arguments are errors (including duplicates introduced via named splat).
+  - unknown named parameters are errors.
+  - variadic parameter itself cannot be passed as a named argument (`fun g(args..., tail)` then `g(args: ...)` is invalid).
+- Trailing block + named arguments:
+  - if the last callable parameter is already provided by name in parentheses, adding a trailing block is invalid.
+
+## 4. Operators (implemented)
+- Assignment: `=`, `+=`, `-=`, `*=`, `/=`, `%=`, `?=`.
+- Logical: `||`, `&&`, unary `!`.
+- Bitwise: `|`, `^`, `&`, `~`, shifts `<<`, `>>`.
+- Equality/comparison: `==`, `!=`, `===`, `!==`, `<`, `<=`, `>`, `>=`, `<=>`, `=~`, `!~`.
+- Type/containment: `is`, `!is`, `in`, `!in`, `as`, `as?`.
+- Null-safe family:
+  - member access: `?.`
+  - safe index: `?[i]`
+  - safe invoke: `?(...)`
+  - safe block invoke: `?{ ... }`
+  - elvis: `?:` and `??`.
+- Increment/decrement: prefix and postfix `++`, `--`.
+
+## 5. Declarations
+- Variables:
+  - `val` immutable, `var` mutable.
+  - top-level/local `val` must be initialized.
+  - class `val` may be late-initialized, but must be assigned in class body/init before class parse ends.
+  - destructuring declaration: `val [a, b, rest...] = expr`.
+  - destructuring declaration details:
+    - allowed in `val` and `var` declarations.
+    - supports nested patterns: `val [a, [b, c...], d] = rhs`.
+    - supports at most one splat (`...`) per pattern level.
+    - RHS must be a `List`.
+    - without splat: RHS must have at least as many elements as pattern arity.
+    - with splat: head/tail elements are bound directly, splat receives a `List`.
+- Functions:
+  - `fun` and `fn` are equivalent.
+  - full body: `fun f(x) { ... }`
+  - shorthand: `fun f(x) = expr`.
+  - generics: `fun f<T>(x: T): T`.
+  - extension functions: `fun Type.name(...) { ... }`.
+  - delegated callable: `fun f(...) by delegate`.
+- Type aliases:
+  - `type Name = TypeExpr`
+  - generic: `type Box<T> = List<T>`
+  - aliases are expanded structurally.
+- Classes/objects/enums/interfaces:
+  - `interface` is parsed as abstract class synonym.
+  - `object` supports named singleton and anonymous object expression forms.
+  - enums support lifted entries: `enum E* { A, B }`.
+  - multiple inheritance is supported; override is enforced when overriding base members.
+- Properties/accessors in class body:
+  - accessor form supports `get`/`set`, including `private set`/`protected set`.
+
+## 6. Control Flow
+- `if` is expression-like.
+- `when(value) { ... }` supported.
+  - branch conditions support equality, `in`, `!in`, `is`, `!is`, and `nullable` predicate.
+  - `when { ... }` (subject-less) is currently not implemented.
+- Loops: `for`, `while`, `do ... while`.
+  - loop `else` blocks are supported.
+  - `break value` can return a loop result.
+- Exceptions: `try/catch/finally`, `throw`.
+
+## 6.1 Destructuring Assignment (implemented)
+- Reassignment form is supported (not only declaration):
+  - `[x, y] = [y, x]`
+- Semantics match destructuring declaration:
+  - nested patterns allowed.
+  - at most one splat per pattern level.
+  - RHS must be a `List`.
+  - too few RHS elements raises runtime error.
+- Targets in pattern are variables parsed from identifier patterns.
+
+## 7. Type System (current behavior)
+- Non-null by default (`T`), nullable with `T?`.
+- `as` (checked cast), `as?` (safe cast returning `null`), `!!` non-null assertion.
+- Type expressions support:
+  - unions `A | B`
+  - intersections `A & B`
+  - function types `(A, B)->R` and receiver form `Receiver.(A)->R`
+  - variadics in function type via ellipsis (`T...`)
+- Generics:
+  - type params on classes/functions/type aliases
+  - bounds via `:` with union/intersection expressions
+  - declaration-site variance via `in` / `out`
+- Generic function/class/type syntax examples:
+  - function: `fun choose<T>(a: T, b: T): T = a`
+  - class: `class Box<T>(val value: T)`
+  - alias: `type PairList<T> = List<List<T>>`
+- Untyped params default to `Object` (`x`) or `Object?` (`x?` shorthand).
+- Untyped `var x` starts as `Unset`; first assignment fixes type tracking in compiler.
+
+## 7.1 Generics Runtime Model and Bounds (AI-critical)
+- Lyng generic type information is operational in script execution contexts; do not assume JVM-style full erasure.
+- Generic call type arguments can be:
+  - explicit at call site (`f<Int>(1)` style),
+  - inferred from runtime values/declared arg types,
+  - defaulted from type parameter defaults (or `Any` fallback).
+- At function execution, generic type parameters are runtime-bound as constants in scope:
+  - simple non-null class-like types are bound as `ObjClass`,
+  - complex/nullable/union/intersection forms are bound as `ObjTypeExpr`.
+- Practical implication for generated code:
+  - inside generic code, treat type params as usable type objects in `is`/`in`/type-expression logic (not as purely compile-time placeholders).
+  - example pattern: `if (value is T) { ... }`.
+- Bound syntax (implemented):
+  - intersection bound: `fun f<T: A & B>(x: T) { ... }`
+  - union bound: `fun g<T: A | B>(x: T) { ... }`
+- Bound checks happen at two points:
+  - compile-time call checking for resolvable generic calls,
+  - runtime re-check while binding type params for actual invocation.
+- Bound satisfaction is currently class-hierarchy based for class-resolvable parts (including union/intersection combination rules).
+- Keep expectations realistic:
+  - extern-generic runtime ABI for full instance-level generic metadata is still proposal-level (`proposals/extern_generic_runtime_abi.md`), so avoid assuming fully materialized generic-instance metadata everywhere.
+
+## 7.2 Differences vs Java / Kotlin / Scala
+- Java:
+  - Java generics are erased at runtime (except reflection metadata and raw `Class` tokens).
+  - Lyng generic params in script execution are runtime-bound type objects, so generated code can reason about `T` directly.
+- Kotlin:
+  - Kotlin on JVM is mostly erased; full runtime type access usually needs `inline reified`.
+  - Lyng generic function execution binds `T` without requiring an inline/reified escape hatch.
+- Scala:
+  - Scala has richer static typing but still runs on JVM erasure model unless carrying explicit runtime evidence (`TypeTag`, etc.).
+  - Lyng exposes runtime-bound type expressions/classes directly in generic execution scope.
+- AI generation rule:
+  - do not port JVM-language assumptions like “`T` unavailable at runtime unless reified/tagged”.
+  - in Lyng, prefer direct type-expression-driven branching when useful, but avoid assuming extern object generic args are always introspectable today.
+
+## 8. OOP, Members, and Dispatch
+- Multiple inheritance with C3-style linearization behavior is implemented in class machinery.
+- Disambiguation helpers are supported:
+  - qualified this: `this@Base.member()`
+  - cast view: `(obj as Base).member()`
+- On unknown receiver types, compiler allows only Object-safe members:
+  - `toString`, `toInspectString`, `let`, `also`, `apply`, `run`
+- Other members require known receiver type or explicit cast.
+
+## 9. Delegation (`by`)
+- Works for `val`, `var`, and `fun`.
+- Expected delegate hooks in practice:
+  - `getValue(thisRef, name)`
+  - `setValue(thisRef, name, newValue)`
+  - `invoke(thisRef, name, args...)` for delegated callables
+  - optional `bind(name, access, thisRef)`
+- `@Transient` is recognized for declarations/params and affects serialization/equality behavior.
+
+## 10. Modules and Imports
+- `package` and `import module.name` are supported.
+- Import form is module-only (no aliasing/selective import syntax in parser).
+- Default module ecosystem includes:
+  - auto-seeded: `lyng.stdlib`
+  - available by import: `lyng.observable`, `lyng.buffer`, `lyng.serialization`, `lyng.time`
+  - extra module (when installed): `lyng.io.fs`, `lyng.io.process`
+
+## 11. Current Limitations / Avoid
+- No subject-less `when { ... }` yet.
+- No regex literal tokenization (`/.../`); use `Regex("...")` or `"...".re`.
+- Do not generate runtime name fallback patterns from legacy docs.

docs/ai_notes_wasm_generation_bug.md

@@ -0,0 +1,15 @@
+# AI notes: avoid Kotlin/Wasm invalid IR with suspend lambdas
+
+## Do
+- Prefer explicit `object : Statement()` with `override suspend fun execute(...)` when building compiler statements.
+- Keep `Statement` objects non-lambda, especially in compiler hot paths like parsing/var declarations.
+- If you need conditional behavior, return early in `execute` instead of wrapping `parseExpression()` with `statement(...) { ... }`.
+- When wasmJs tests hang in the browser, first check `wasmJsNodeTest` for a compile error; hangs often mean module instantiation failed.
+
+## Don't
+- Do not create suspend lambdas inside `Statement` factories (`statement { ... }`) for wasm targets.
+- Do not "fix" hangs by increasing browser timeouts; it masks invalid wasm generation.
+
+## Debugging tips
+- Look for `$invokeCOROUTINE$` in wasm function names when mapping failures.
+- If node test logs a wasm compile error, the browser hang is likely the same root cause.

docs/ai_stdlib_reference.md

@@ -0,0 +1,75 @@
+# Lyng Stdlib Reference for AI Agents (Compact)
+
+Purpose: fast overview of what is available by default and what must be imported.
+
+Sources: `lynglib/src/commonMain/kotlin/net/sergeych/lyng/Script.kt`, `lynglib/stdlib/lyng/root.lyng`, `lynglib/src/commonMain/kotlin/net/sergeych/lyng/stdlib_included/observable_lyng.kt`.
+
+## 1. Default Availability
+- Normal scripts are auto-seeded with `lyng.stdlib` (default import manager path).
+- Root runtime scope also exposes global constants/functions directly.
+
+## 2. Core Global Functions (Root Scope)
+- IO/debug: `print`, `println`, `traceScope`.
+- Invocation/util: `call`, `run`, `dynamic`, `cached`, `lazy`.
+- Assertions/tests: `assert`, `assertEquals`/`assertEqual`, `assertNotEquals`, `assertThrows`.
+- Preconditions: `require`, `check`.
+- Async/concurrency: `launch`, `yield`, `flow`, `delay`.
+- Math: `floor`, `ceil`, `round`, `sin`, `cos`, `tan`, `asin`, `acos`, `atan`, `sinh`, `cosh`, `tanh`, `asinh`, `acosh`, `atanh`, `exp`, `ln`, `log10`, `log2`, `pow`, `sqrt`, `abs`, `clamp`.
+
+## 3. Core Global Constants/Types
+- Values: `Unset`, `π`.
+- Primitive/class symbols: `Object`, `Int`, `Real`, `Bool`, `Char`, `String`, `Class`, `Callable`.
+- Collections/types: `Iterable`, `Iterator`, `Collection`, `Array`, `List`, `ImmutableList`, `Set`, `ImmutableSet`, `Map`, `ImmutableMap`, `MapEntry`, `Range`, `RingBuffer`.
+- Random: singleton `Random` and class `SeededRandom`.
+- Async types: `Deferred`, `CompletableDeferred`, `Mutex`, `Flow`, `FlowBuilder`.
+- Delegation types: `Delegate`, `DelegateContext`.
+- Regex types: `Regex`, `RegexMatch`.
+- Also present: `Math.PI` namespace constant.
+
+## 4. `lyng.stdlib` Module Surface (from `root.lyng`)
+### 4.1 Extern class declarations
+- Exceptions/delegation base: `Exception`, `IllegalArgumentException`, `NotImplementedException`, `Delegate`.
+- Collections and iterables: `Iterable<T>`, `Iterator<T>`, `Collection<T>`, `Array<T>`, `List<T>`, `ImmutableList<T>`, `Set<T>`, `ImmutableSet<T>`, `Map<K,V>`, `ImmutableMap<K,V>`, `MapEntry<K,V>`, `RingBuffer<T>`.
+- Host iterator bridge: `KotlinIterator<T>`.
+- Random APIs: `extern object Random`, `extern class SeededRandom`.
+
+### 4.2 High-use extension APIs
+- Iteration/filtering: `forEach`, `filter`, `filterFlow`, `filterNotNull`, `filterFlowNotNull`, `drop`, `dropLast`, `takeLast`.
+- Search/predicates: `findFirst`, `findFirstOrNull`, `any`, `all`, `count`, `first`, `last`.
+- Mapping/aggregation: `map`, `flatMap`, `flatten`, `sum`, `sumOf`, `minOf`, `maxOf`.
+- Ordering: `sorted`, `sortedBy`, `shuffled`, `List.sort`, `List.sortBy`.
+- String helper: `joinToString`, `String.re`.
+
+### 4.3 Delegation helpers
+- `enum DelegateAccess { Val, Var, Callable }`
+- `interface Delegate<T,ThisRefType=void>` with `getValue`, `setValue`, `invoke`, `bind`.
+- `class lazy<T,...>` delegate implementation.
+- `fun with(self, block)` helper.
+
+### 4.4 Other module-level symbols
+- `$~` (last regex match object).
+- `TODO(message?)` utility.
+- `StackTraceEntry` class.
+- `Random.nextInt()`, `Random.nextFloat()`, `Random.next(range)`, `Random.seeded(seed)`.
+- `SeededRandom.nextInt()`, `SeededRandom.nextFloat()`, `SeededRandom.next(range)`.
+
+## 5. Additional Built-in Modules (import explicitly)
+- `import lyng.observable`
+  - `Observable`, `Subscription`, `ObservableList`, `ListChange` and change subtypes, `ChangeRejectionException`.
+- `import lyng.buffer`
+  - `Buffer`, `MutableBuffer`.
+- `import lyng.serialization`
+  - `Lynon` serialization utilities.
+- `import lyng.time`
+  - `Instant`, `DateTime`, `Duration`, and module `delay`.
+
+## 6. Optional (lyngio) Modules
+Requires installing `lyngio` into the import manager from host code.
+- `import lyng.io.fs` (filesystem `Path` API)
+- `import lyng.io.process` (process execution API)
+- `import lyng.io.console` (console capabilities, geometry, ANSI/output, events)
+
+## 7. AI Generation Tips
+- Assume `lyng.stdlib` APIs exist in regular script contexts.
+- For platform-sensitive code (`fs`, `process`, `console`), gate assumptions and mention required module install.
+- Prefer extension-method style (`items.filter { ... }`) and standard scope helpers (`let`/`also`/`apply`/`run`).

docs/class_reference.md

@@ -1,24 +0,0 @@
-# Classes
-
-## Declaring
-
-    class Foo1
-    class Foo2() // same, empty constructor
-    class Foo3() { // full
-    }
-    class Foo4 { // Only body
-    }
-
-```
-class_declaration = ["abstract",] "class" [, constructor] [, body]
-constructor = "(", [field [, field]] ")
-field = [visibility ,] [access ,] name [, typedecl]
-body = [visibility] ("var", vardecl) | ("val", vardecl) | ("fun", fundecl)
-visibility = "private" | "protected" | "internal"
-```
-
-### Abstract classes
-
-Contain one pr more abstract methods which must be implemented; though they
-can have constructors, the instances of the abstract classes could not be
-created independently

docs/declaring_arguments.md

@@ -1,11 +1,13 @@
 # Declaring arguments in Lyng
 
+[//]: # (topMenu)
+
 It is a common thing that occurs in many places in Lyng, function declarations, 
 lambdas and class declarations.
 
 ## Regular
 
-## default values
+## Default values
 
 Default parameters should not be mixed with mandatory ones:
 
@@ -32,13 +34,18 @@ Valid examples:
 
 Ellipsis are used to declare variadic arguments. It basically means "all the arguments available here". It means, ellipsis argument could be in any part of the list, being, end or middle, but there could be only one ellipsis argument and it must not have default value, its default value is always `[]`, en empty list.
 
+Ellipsis can also appear in **function types** to denote a variadic position:
+
+    var f: (Int, Object..., String)->Real
+    var anyArgs: (...)->Int   // shorthand for (Object...)->Int
+
 Ellipsis argument receives what is left from arguments after processing regular one that could be before or after.
 
 Ellipsis could be a first argument:
 
     fun testCountArgs(data...,size) {
         assert(size is Int)
-        assertEquals(size, data.size)
+        assertEquals(size, (data as List).size)
     }
     testCountArgs( 1, 2, "three", 3)
     >>> void
@@ -47,7 +54,7 @@ Ellipsis could also be a last one:
 
     fun testCountArgs(size, data...) {
         assert(size is Int)
-        assertEquals(size, data.size)
+        assertEquals(size, (data as List).size)
     }
     testCountArgs( 3, 10, 2, "three")
     >>> void
@@ -56,7 +63,7 @@ Or in the middle:
 
     fun testCountArgs(size, data..., textToReturn) {
         assert(size is Int)
-        assertEquals(size, data.size)
+        assertEquals(size, (data as List).size)
         textToReturn
     }
     testCountArgs( 3, 10, 2, "three", "All OK")
@@ -73,6 +80,13 @@ destructuring arrays when calling functions and lambdas:
     getFirstAndLast( ...(1..10) ) // see "splats" section below
     >>> [1,10]
 
+Note that array destructuring can also be used in assignments:
+
+    val [first, middle..., last] = [1, 2, 3, 4, 5]
+    [x, y] = [y, x] // Swap
+
+See [tutorial] and [List] documentation for more details on destructuring assignments.
+
 # Splats
 
 Ellipsis allows to convert argument lists to lists. The inversa algorithm that converts [List],
@@ -96,5 +110,73 @@ There could be any number of splats at any positions. You can splat any other [I
     >>> [start,1,2,3,end]
     >>> void
 
+## Named arguments in calls
+
+Lyng supports named arguments at call sites using colon syntax `name: value`. 
+
+### Shorthand for Named Arguments
+
+If you want to pass a variable as a named argument and the variable has the same name as the parameter, you can omit the value and use the shorthand `name:`. This is highly readable and matches the shorthand for map literals.
+
+```lyng
+    fun test(a, b, c) { [a, b, c] }
+    
+    val a = 1
+    val b = 2
+    val c = 3
+    
+    // Explicit:
+    assertEquals([1, 2, 3], test(a: a, b: b, c: c))
+    
+    // Shorthand (preferred):
+    assertEquals([1, 2, 3], test(a:, b:, c:))
+```
+
+This shorthand is elegant, reduces boilerplate, and is consistent with Lyng's map literal syntax. It works for both function calls and class constructors.
+
+Rules for named arguments:
+
+- Named arguments must follow positional arguments. After the first named argument, no positional arguments may appear inside the parentheses.
+- The only exception is the syntactic trailing block after the call: `f(args) { ... }`. This block is outside the parentheses and is handled specially (see below).
+- A named argument cannot reassign a parameter already set positionally.
+- If the last parameter has already been assigned by a named argument (or named splat), a trailing block is not allowed and results in an error.
+
+Why `:` and not `=` at call sites? In Lyng, `=` is an expression (assignment), so we use `:` to avoid ambiguity. This is a key difference from **Kotlin**, which uses `=` for named arguments. Declarations in Lyng continue to use `:` for types, while call sites use `as` / `as?` for type operations.
+
+## Named splats (map splats)
+
+Splat (`...`) of a Map provides named arguments to the call. Only string keys are allowed. You can use the same auto-substitution shorthand inside map literals used for splats:
+
+```lyng
+    fun test(a="a", b="b", c="c", d="d") { [a, b, c, d] }
+    
+    val b = "B!"
+    val d = "D!"
+    
+    // Auto-substitution in map literal:
+    val patch = { d:, b: }
+    
+    val r = test("A?", ...patch)
+    assertEquals(["A?","B!","c","D!"], r)
+```
+
+Constraints:
+
+- Map splat keys must be strings; otherwise, a clean error is thrown.
+- Named splats cannot duplicate parameters already assigned (by positional or named arguments).
+- Named splats must follow all positional arguments and positional splats.
+- Ellipsis parameters (variadic) remain positional-only and cannot be assigned by name.
+
+## Trailing-lambda rule interaction
+
+If a call is immediately followed by a block `{ ... }`, it is treated as an extra last argument and bound to the last parameter. However, if the last parameter is already assigned by a named argument or a named splat, using a trailing block is an error:
+
+```lyng
+    fun f(x, onDone) { onDone(x) }
+    f(x: 1) { 42 }   // ERROR
+    f(1) { 42 }      // OK
+```
+    
 
 [tutorial]: tutorial.md
+[List]: List.md

docs/delegation.md

@@ -0,0 +1,194 @@
+# Delegation in Lyng
+
+Delegation is a powerful pattern that allows you to outsource the logic of properties (`val`, `var`) and functions (`fun`) to another object. This enables code reuse, separation of concerns, and the implementation of common patterns like lazy initialization, observable properties, and remote procedure calls (RPC) with minimal boilerplate.
+
+## The `by` Keyword
+
+Delegation is triggered using the `by` keyword in a declaration. The expression following `by` is evaluated once when the member is initialized, and the resulting object becomes the **delegate**.
+
+```lyng
+val x by MyDelegate()
+var y by MyDelegate()
+fun f by MyDelegate()
+```
+
+## The Unified Delegate Model
+
+A delegate object can implement any of the following methods to intercept member access. All methods receive the `thisRef` (the instance containing the member) and the `name` of the member.
+
+```lyng
+interface Delegate {
+    // Called when a 'val' or 'var' is read
+    fun getValue(thisRef, name)
+    
+    // Called when a 'var' is assigned
+    fun setValue(thisRef, name, newValue)
+    
+    // Called when a 'fun' is invoked
+    fun invoke(thisRef, name, args...)
+    
+    // Optional: Called once during initialization to "bind" the delegate
+    // Can be used for validation or to return a different delegate instance
+    fun bind(name, access, thisRef) = this
+}
+```
+
+### Delegate Access Types
+
+The `bind` method receives an `access` parameter of type `DelegateAccess`, which can be one of:
+- `DelegateAccess.Val`
+- `DelegateAccess.Var`
+- `DelegateAccess.Callable` (for `fun`)
+
+## Usage Cases and Examples
+
+### 1. Lazy Initialization
+
+The classic `lazy` pattern ensures a value is computed only when first accessed and then cached. In Lyng, `lazy` is implemented as a class that follows this pattern. While classes typically start with an uppercase letter, `lazy` is an exception to make its usage feel like a native language feature.
+
+```lyng
+class lazy(val creator) : Delegate {
+    private var value = Unset
+
+    override fun bind(name, access, thisRef) {
+        if (access != DelegateAccess.Val) throw "lazy delegate can only be used with 'val'"
+        this
+    }
+
+    override fun getValue(thisRef, name) {
+        if (value == Unset) {
+            // calculate value using thisRef as this:
+            value = with(thisRef) creator()
+        }
+        value
+    }
+}
+
+// Usage:
+val expensiveData by lazy {
+    println("Performing expensive computation...")
+    42
+}
+
+println(expensiveData) // Computes and prints 42
+println(expensiveData) // Returns 42 immediately
+```
+
+### 2. Observable Properties
+
+Delegates can be used to react to property changes.
+
+```lyng
+class Observable(initialValue, val onChange) {
+    private var value = initialValue
+
+    fun getValue(thisRef, name) = value
+    
+    fun setValue(thisRef, name, newValue) {
+        val oldValue = value
+        value = newValue
+        onChange(name, oldValue, newValue)
+    }
+}
+
+class User {
+    var name by Observable("Guest") { name, old, new ->
+        println("Property %s changed from %s to %s"(name, old, new))
+    }
+}
+
+val u = User()
+u.name = "Alice" // Prints: Property name changed from Guest to Alice
+```
+
+### 3. Function Delegation (Proxies)
+
+You can delegate an entire function to an object. This is particularly useful for implementing decorators or RPC clients.
+
+```lyng
+object LoggerDelegate {
+    fun invoke(thisRef, name, args...) {
+        println("Calling function: " + name + " with args: " + args)
+        // Logic here...
+        "Result of " + name
+    }
+}
+
+fun remoteAction by LoggerDelegate
+
+println(remoteAction(1, 2, 3))
+// Prints: Calling function: remoteAction with args: [1, 2, 3]
+// Prints: Result of remoteAction
+```
+
+### 4. Stateless Delegates (Shared Singletons)
+
+Because `getValue`, `setValue`, and `invoke` receive `thisRef`, a single object can act as a delegate for multiple properties across many instances without any per-property memory overhead.
+
+```lyng
+object Constant42 {
+    fun getValue(thisRef, name) = 42
+}
+
+class Foo {
+    val a by Constant42
+    val b by Constant42
+}
+
+val f = Foo()
+assertEquals(42, f.a)
+assertEquals(42, f.b)
+```
+
+### 5. Local Delegation
+
+Delegation is not limited to class members; you can also use it for local variables inside functions.
+
+```lyng
+fun test() {
+    val x by LocalProxy(123)
+    println(x)
+}
+```
+
+### 6. Map as a Delegate
+
+Maps can be used as delegates for `val` and `var` properties. When a map is used as a delegate, it uses the property name as a key to read from or write to the map.
+
+```lyng
+val m = { "a": 1, "b": 2 }
+val a by m
+var b by m
+
+println(a) // 1
+println(b) // 2
+
+b = 42
+println(m["b"]) // 42
+```
+
+Because `Map` implements `getValue` and `setValue`, it works seamlessly with any object that needs to store its properties in a map (e.g., when implementing dynamic schemas or JSON-backed objects).
+
+## The `bind` Hook
+
+The `bind(name, access, thisRef)` method is called exactly once when the member is being initialized. It allows the delegate to:
+1.  **Validate usage**: Throw an error if the delegate is used with the wrong member type (e.g., `lazy` on a `var`).
+2.  **Initialize state**: Set up internal state based on the property name or the containing instance.
+3.  **Substitute itself**: Return a different object that will act as the actual delegate.
+
+```lyng
+class ValidatedDelegate() {
+    fun bind(name, access, thisRef) {
+        if (access == DelegateAccess.Var) {
+            throw "This delegate cannot be used with 'var'"
+        }
+        this
+    }
+    
+    fun getValue(thisRef, name) = "Validated"
+}
+```
+
+## Summary
+
+Delegation in Lyng combines the elegance of Kotlin-style properties with the flexibility of dynamic function interception. By unifying `val`, `var`, and `fun` delegation into a single model, Lyng provides a consistent and powerful tool for meta-programming and code reuse.

docs/embedding.md

@@ -0,0 +1,567 @@
+# Embedding Lyng in your Kotlin project
+
+Lyng is a tiny, embeddable, Kotlin‑first scripting language. This page shows, step by step, how to:
+
+- add Lyng to your build
+- create a runtime and execute scripts
+- declare extern globals in Lyng and bind them from Kotlin
+- read variable values back in Kotlin
+- call Lyng functions from Kotlin
+- create your own packages and import them in Lyng
+
+All snippets below use idiomatic Kotlin and rely on Lyng public APIs. They work on JVM and other Kotlin Multiplatform targets supported by `lynglib`.
+
+Note: all Lyng APIs shown are `suspend`, because script evaluation is coroutine‑friendly and can suspend.
+
+### 1) Add Lyng to your build
+
+Add the repository where you publish Lyng artifacts and the dependency on the core library `lynglib`.
+
+Gradle Kotlin DSL (build.gradle.kts):
+
+```kotlin
+repositories {
+    // Your standard repos
+    mavenCentral()
+
+    // If you publish to your own Maven (example: Gitea packages). Adjust URL/token as needed.
+    maven(url = uri("https://gitea.sergeych.net/api/packages/SergeychWorks/maven"))
+}
+
+dependencies {
+    // Multiplatform: place in appropriate source set if needed
+    implementation("net.sergeych:lynglib:1.0.0-SNAPSHOT")
+}
+```
+
+If you use Kotlin Multiplatform, add the dependency in the `commonMain` source set (and platform‑specific sets if you need platform APIs).
+
+### 2) Create a runtime (Scope) and execute scripts
+
+The easiest way to get a ready‑to‑use scope with standard packages is via `Script.newScope()`.
+
+```kotlin
+fun main() = kotlinx.coroutines.runBlocking {
+    val scope = Script.newScope() // suspends on first init
+
+    // Evaluate a one‑liner
+    val result = scope.eval("1 + 2 * 3")
+    println("Lyng result: $result") // ObjReal/ObjInt etc.
+}
+```
+
+You can also pre‑compile a script and execute it multiple times:
+
+```kotlin
+val script = Compiler.compile("""
+    // any Lyng code
+    val x = 40 + 2
+    x
+""")
+
+val run1 = script.execute(scope)
+val run2 = script.execute(scope)
+```
+
+`Scope.eval("...")` is a shortcut that compiles and executes on the given scope.
+
+### 3) Preferred: bind extern globals from Kotlin
+
+For module-level APIs, the default workflow is:
+
+1. declare globals in Lyng using `extern fun` / `extern val` / `extern var`;
+2. bind Kotlin implementation via `ModuleScope.globalBinder()`.
+
+```kotlin
+import net.sergeych.lyng.bridge.*
+import net.sergeych.lyng.obj.ObjInt
+import net.sergeych.lyng.obj.ObjString
+
+val im = Script.defaultImportManager.copy()
+im.addPackage("my.api") { module ->
+    module.eval("""
+        extern fun globalFun(v: Int): Int
+        extern var globalProp: String
+        extern val globalVersion: String
+    """.trimIndent())
+
+    val binder = module.globalBinder()
+
+    binder.bindGlobalFun1<Int>("globalFun") { v ->
+        ObjInt.of((v + 1).toLong())
+    }
+
+    var prop = "initial"
+    binder.bindGlobalVar(
+        name = "globalProp",
+        get = { prop },
+        set = { prop = it }
+    )
+
+    binder.bindGlobalVar(
+        name = "globalVersion",
+        get = { "1.0.0" } // readonly: setter omitted
+    )
+}
+```
+
+Usage from Lyng:
+
+```lyng
+import my.api
+
+assertEquals(42, globalFun(41))
+assertEquals("initial", globalProp)
+globalProp = "changed"
+assertEquals("changed", globalProp)
+assertEquals("1.0.0", globalVersion)
+```
+
+For custom argument handling and full runtime access:
+
+```kotlin
+binder.bindGlobalFun("sum3") {
+    requireExactCount(3)
+    ObjInt.of((int(0) + int(1) + int(2)).toLong())
+}
+
+binder.bindGlobalFunRaw("echoRaw") { _, args ->
+    args.firstAndOnly()
+}
+```
+
+### 4) Low-level: direct functions/variables from Kotlin
+
+Use this when you intentionally want raw `Scope` APIs. For most module APIs, prefer section 3.
+
+```kotlin
+// A function returning value
+scope.addFn<ObjInt>("inc") {
+    val x = args.firstAndOnly() as ObjInt
+    ObjInt(x.value + 1)
+}
+
+// A void function (returns Lyng Void)
+scope.addVoidFn("log") {
+    val items = args.list // List<Obj>
+    println(items.joinToString(" ") { it.toString(this).value })
+}
+
+// When adding a member function to a class, you can use isOverride = true
+// myClass.addFn("toString", isOverride = true) {
+//     ObjString("Custom string representation")
+// }
+
+// Call them from Lyng
+scope.eval("val y = inc(41); log('Answer:', y)")
+```
+
+You can register multiple names (aliases) at once: `addFn<ObjInt>("inc", "increment") { ... }`.
+
+Scope-backed Kotlin lambdas receive a `ScopeFacade` (not a full `Scope`). For migration and convenience, these utilities are available on the facade:
+
+- Access: `args`, `pos`, `thisObj`, `get(name)`
+- Invocation: `call(...)`, `resolve(...)`, `assign(...)`, `toStringOf(...)`, `inspect(...)`, `trace(...)`
+- Args helpers: `requiredArg<T>()`, `requireOnlyArg<T>()`, `requireExactCount(...)`, `requireNoArgs()`, `thisAs<T>()`
+- Errors: `raiseError(...)`, `raiseClassCastError(...)`, `raiseIllegalArgument(...)`, `raiseIllegalState(...)`, `raiseNoSuchElement(...)`,
+  `raiseSymbolNotFound(...)`, `raiseNotImplemented(...)`, `raiseNPE()`, `raiseIndexOutOfBounds(...)`, `raiseIllegalAssignment(...)`,
+  `raiseUnset(...)`, `raiseNotFound(...)`, `raiseAssertionFailed(...)`, `raiseIllegalOperation(...)`, `raiseIterationFinished()`
+
+If you truly need the full `Scope` (e.g., for low-level interop), use `requireScope()` explicitly.
+
+### 5) Add Kotlin‑backed fields
+
+If you need a simple field (with a value) instead of a computed property, use `createField`. This adds a field to the class that will be present in all its instances.
+
+```kotlin
+val myClass = ObjClass("MyClass")
+
+// Add a read-only field (constant)
+myClass.createField("version", ObjString("1.0.0"), isMutable = false)
+
+// Add a mutable field with an initial value
+myClass.createField("count", ObjInt(0), isMutable = true)
+
+// If you are overriding a field from a base class, use isOverride = true
+// myClass.createField("someBaseField", ObjInt(42), isOverride = true)
+
+scope.addConst("MyClass", myClass)
+```
+
+In Lyng:
+```lyng
+val instance = MyClass()
+println(instance.version) // -> "1.0.0"
+instance.count = 5
+println(instance.count)   // -> 5
+```
+
+### 6) Add Kotlin‑backed properties
+
+Properties in Lyng are pure accessors (getters and setters) and do not have automatic backing fields. You can add them to a class using `addProperty`.
+
+```kotlin
+val myClass = ObjClass("MyClass")
+var internalValue: Long = 10
+
+myClass.addProperty(
+    name = "value",
+    getter = { 
+        // Return current value as a Lyng object
+        ObjInt(internalValue) 
+    },
+    setter = { newValue ->
+        // newValue is passed as a Lyng object (the first and only argument)
+        internalValue = (newValue as ObjInt).value
+    }
+)
+
+// You can also create an ObjProperty explicitly
+val explicitProp = ObjProperty(
+    name = "hexValue",
+    getter = statement { ObjString(internalValue.toString(16)) }
+)
+myClass.addProperty("hexValue", prop = explicitProp)
+
+// Use isOverride = true when overriding a property from a base class
+// myClass.addProperty("baseProp", getter = { ... }, isOverride = true)
+
+scope.addConst("MyClass", myClass)
+```
+
+Usage in Lyng:
+```lyng
+val instance = MyClass()
+println(instance.value) // -> 10
+instance.value = 42
+println(instance.value) // -> 42
+```
+
+### 6.5) Preferred: bind Kotlin implementations to declared Lyng classes
+
+For extensions and libraries, the **preferred** workflow is Lyng‑first: declare the class and its members in Lyng, then bind the Kotlin implementations using the bridge.
+
+This keeps Lyng semantics (visibility, overrides, type checks) in Lyng, while Kotlin supplies the behavior.
+
+Pure extern declarations use the simplified rule set:
+- `extern class` / `extern object` are declaration-only ABI surfaces.
+- Every member in their body is implicitly extern (you may still write `extern`, but it is redundant).
+- Plain Lyng member implementations inside `extern class` / `extern object` are not allowed.
+- Put Lyng behavior into regular classes or extension methods.
+
+```lyng
+// Lyng side (in a module)
+class Counter {
+    extern var value: Int
+    extern fun inc(by: Int): Int
+}
+```
+
+Note: members of `extern class` / `extern object` are treated as extern by default, so the compiler emits ABI slots that Kotlin bindings attach to. This applies to functions and properties bound via `addFun` / `addVal` / `addVar`.
+
+Example of pure extern class declaration:
+
+```lyng
+extern class HostCounter {
+    var value: Int
+    fun inc(by: Int): Int
+}
+```
+
+If you need Lyng-side convenience behavior, add it as an extension:
+
+```lyng
+fun HostCounter.bump() = inc(1)
+```
+
+```kotlin
+// Kotlin side (binding)
+val moduleScope = Script.newScope() // or an existing module scope
+moduleScope.eval("class Counter { extern var value: Int; extern fun inc(by: Int): Int }")
+
+moduleScope.bind("Counter") {
+    addVar(
+        name = "value",
+        get = { thisObj.readField(this, "value").value },
+        set = { v -> thisObj.writeField(this, "value", v) }
+    )
+    addFun("inc") {
+        val by = args.requiredArg<ObjInt>(0).value
+        val current = thisObj.readField(this, "value").value as ObjInt
+        val next = ObjInt(current.value + by)
+        thisObj.writeField(this, "value", next)
+        next
+    }
+}
+```
+
+Notes:
+
+- Binding must happen **before** the first instance is created.
+- Use [LyngClassBridge] to bind by name/module, or by an already resolved `ObjClass`.
+- Use `ObjInstance.data` / `ObjClass.classData` to attach Kotlin‑side state when needed.
+
+### 6.5a) Bind Kotlin implementations to declared Lyng objects
+
+For `extern object` declarations, bind implementations to the singleton instance using `ModuleScope.bindObject`.
+This mirrors class binding but targets an already created object instance.
+As with class binding, you must first add/evaluate the Lyng declaration into that module scope, then bind Kotlin handlers.
+
+```kotlin
+// Kotlin side (binding)
+val moduleScope = importManager.createModuleScope(Pos.builtIn, "bridge.obj")
+
+// 1) Seed the module with the Lyng declaration first
+moduleScope.eval("""
+    extern object HostObject {
+        extern fun add(a: Int, b: Int): Int
+        extern val status: String
+        extern var count: Int
+    }
+""".trimIndent())
+
+// 2) Then bind Kotlin implementations to that declared object
+moduleScope.bindObject("HostObject") {
+    classData = "OK"
+    init { _ -> data = 0L }
+    addFun("add") {
+        val a = args.requiredArg<ObjInt>(0).value
+        val b = args.requiredArg<ObjInt>(1).value
+        ObjInt.of(a + b)
+    }
+    addVal("status") { ObjString(classData as String) }
+    addVar(
+        "count",
+        get = { ObjInt.of((thisObj as ObjInstance).data as Long) },
+        set = { value -> (thisObj as ObjInstance).data = (value as ObjInt).value }
+    )
+}
+```
+
+Notes:
+
+- Required order: declare/eval Lyng object in the module first, then call `bindObject(...)`.
+  This is the pattern covered by `BridgeBindingTest.testExternObjectBinding`.
+- Members must be extern (explicitly, or implicitly via `extern object`) so the compiler emits ABI slots for Kotlin bindings.
+- You can also bind by name/module via `LyngObjectBridge.bind(...)`.
+
+Minimal `extern fun` example:
+
+```kotlin
+val moduleScope = importManager.createModuleScope(Pos.builtIn, "bridge.ping")
+
+moduleScope.eval("""
+    extern object HostObject {
+        extern fun ping(): Int
+    }
+""".trimIndent())
+
+moduleScope.bindObject("HostObject") {
+    addFun("ping") { ObjInt.of(7) }
+}
+```
+
+### 6.6) Preferred: Kotlin reflection bridge for call‑by‑name
+
+For Kotlin code that needs dynamic access to Lyng variables, functions, or members, use the bridge resolver.
+It provides explicit, cached handles and predictable lookup rules.
+
+```kotlin
+val scope = Script.newScope()
+scope.eval("""
+    val x = 40
+    fun add(a, b) = a + b
+    class Box { var value = 1 }
+""")
+
+val resolver = scope.resolver()
+
+// Read a top‑level value
+val x = resolver.resolveVal("x").get(scope)
+
+// Call a function by name (cached inside the resolver)
+val sum = (resolver as BridgeCallByName).callByName(scope, "add", Arguments(ObjInt(1), ObjInt(2)))
+
+// Member access
+val box = scope.eval("Box()")
+val valueHandle = resolver.resolveMemberVar(box, "value")
+valueHandle.set(scope, ObjInt(10))
+val value = valueHandle.get(scope)
+```
+
+### 7) Read variable values back in Kotlin
+
+The simplest approach: evaluate an expression that yields the value and convert it.
+
+```kotlin
+val kotlinAnswer = scope.eval("(1 + 2) * 3").toKotlin(scope) // -> 9 (Int)
+
+// After scripts manipulate your vars:
+scope.addOrUpdateItem("name", ObjString("Lyng"))
+scope.eval("name = name + ' rocks!'")
+val kotlinName = scope.eval("name").toKotlin(scope) // -> "Lyng rocks!"
+```
+
+Advanced: you can also grab a variable record directly via `scope.get(name)` and work with its `Obj` value, but evaluating `"name"` is often clearer and enforces Lyng semantics consistently.
+
+### 8) Execute scripts with parameters; call Lyng functions from Kotlin
+
+There are two convenient patterns.
+
+1) Evaluate a Lyng call expression directly:
+
+```kotlin
+// Suppose Lyng defines: fun add(a, b) = a + b
+scope.eval("fun add(a, b) = a + b")
+
+val sum = scope.eval("add(20, 22)").toKotlin(scope) // -> 42
+```
+
+2) Call a Lyng function by name via a prepared call scope:
+
+```kotlin
+// Ensure the function exists in the scope
+scope.eval("fun add(a, b) = a + b")
+
+// Look up the function object
+val addFn = scope.get("add")!!.value as Statement
+
+// Create a child scope with arguments (as Lyng Objs)
+val callScope = scope.createChildScope(
+    args = Arguments(listOf(ObjInt(20), ObjInt(22)))
+)
+
+val resultObj = addFn.execute(callScope)
+val result = resultObj.toKotlin(scope) // -> 42
+```
+
+If you need to pass complex data (lists, maps), construct the corresponding Lyng `Obj` types (`ObjList`, `ObjMap`, etc.) and pass them in `Arguments`.
+
+### 9) Create your own packages and import them in Lyng
+
+Lyng supports packages that are imported from scripts. You can register packages programmatically via `ImportManager` or by providing source texts that declare `package ...`.
+
+Key concepts:
+
+- `ImportManager` holds package registrations and lazily builds `ModuleScope`s when first imported.
+- Every `Scope` has `currentImportProvider` and (if it’s an `ImportManager`) a convenience `importManager` to register packages.
+
+Register a Kotlin‑built package:
+
+```kotlin
+import net.sergeych.lyng.bridge.*
+import net.sergeych.lyng.obj.ObjInt
+
+val scope = Script.newScope()
+
+// Access the import manager behind this scope
+val im: ImportManager = scope.importManager
+
+// Register a package "my.tools"
+im.addPackage("my.tools") { module: ModuleScope ->
+    module.eval(
+        """
+        extern val version: String
+        extern fun triple(x: Int): Int
+        """.trimIndent()
+    )
+    val binder = module.globalBinder()
+    binder.bindGlobalVar(
+        name = "version",
+        get = { "1.0" }
+    )
+    binder.bindGlobalFun1<Int>("triple") { x ->
+        ObjInt.of((x * 3).toLong())
+    }
+}
+
+// Use it from Lyng
+scope.eval("""
+    import my.tools.*
+    val v = triple(14)
+""")
+val v = scope.eval("v").toKotlin(scope) // -> 42
+```
+
+Register a package from Lyng source text:
+
+```kotlin
+val pkgText = """
+    package math.extra
+
+    fun sqr(x) = x * x
+""".trimIndent()
+
+scope.importManager.addTextPackages(pkgText)
+
+scope.eval("""
+    import math.extra.*
+    val s = sqr(12)
+""")
+val s = scope.eval("s").toKotlin(scope) // -> 144
+```
+
+You can also register from parsed `Source` instances via `addSourcePackages(source)`.
+
+### 10) Executing from files, security, and isolation
+
+- To run code from a file, read it and pass to `scope.eval(text)` or compile with `Compiler.compile(Source(fileName, text))`.
+- `ImportManager` takes an optional `SecurityManager` if you need to restrict what packages or operations are available. By default, `Script.defaultImportManager` allows everything suitable for embedded use; clamp it down in sandboxed environments.
+- For isolation, create fresh modules/scopes via `Scope.new()` or `Script.newScope()` when you need a clean environment per request.
+
+```kotlin
+// Fresh module based on the default manager, without the standard prelude
+val isolated = net.sergeych.lyng.Scope.new()
+```
+
+### 11) Tips and troubleshooting
+
+- All values that cross the boundary must be Lyng `Obj` instances. Convert Kotlin values explicitly (e.g., `ObjInt`, `ObjReal`, `ObjString`).
+- Use `toKotlin(scope)` to get Kotlin values back. Collections convert to Kotlin collections recursively.
+- Most public API in Lyng is suspendable. If you are not already in a coroutine, wrap calls in `runBlocking { ... }` on the JVM for quick tests.
+- When registering packages, names must be unique. Register before you compile/evaluate scripts that import them.
+- To debug scope content, `scope.toString()` and `scope.trace()` can help during development.
+
+### 12) Handling and serializing exceptions
+
+When Lyng code throws an exception, it is caught in Kotlin as an `ExecutionError`. This error wraps the actual Lyng `Obj` that was thrown (which could be a built-in `ObjException` or a user-defined `ObjInstance`).
+
+To simplify handling these objects from Kotlin, several extension methods are provided on the `Obj` class. These methods work uniformly regardless of whether the exception is built-in or user-defined.
+
+#### Uniform Exception API
+
+| Method | Description |
+| :--- | :--- |
+| `obj.isLyngException()` | Returns `true` if the object is an instance of `Exception`. |
+| `obj.isInstanceOf("ClassName")` | Returns `true` if the object is an instance of the named Lyng class or its ancestors. |
+| `obj.getLyngExceptionMessage(scope?=null)` | Returns the exception message as a Kotlin `String`. |
+| `obj.getLyngExceptionMessageWithStackTrace(scope?=null)` | Returns a detailed message with a formatted stack trace. |
+| `obj.getLyngExceptionString(scope)` | Returns a formatted string including the class name, message, and primary throw site. |
+| `obj.getLyngExceptionStackTrace(scope)` | Returns the stack trace as an `ObjList` of `StackTraceEntry`. |
+| `obj.getLyngExceptionExtraData(scope)` | Returns the extra data associated with the exception. |
+| `obj.raiseAsExecutionError(scope?=null)` | Rethrows the object as a Kotlin `ExecutionError`. |
+
+#### Example: Serialization and Rethrowing
+
+You can serialize Lyng exception objects using `Lynon` to transmit them across boundaries and then rethrow them.
+
+```kotlin
+try {
+    scope.eval("throw MyUserException(404, \"Not Found\")")
+} catch (e: ExecutionError) {
+    // 1. Serialize the Lyng exception object
+    val encoded: UByteArray = lynonEncodeAny(scope, e.errorObject)
+
+    // ... (transmit 'encoded' byte array) ...
+
+    // 2. Deserialize it back to an Obj in a different context
+    val decoded: Obj = lynonDecodeAny(scope, encoded)
+
+    // 3. Properly rethrow it on the Kotlin side using the uniform API
+    decoded.raiseAsExecutionError(scope)
+}
+```
+
+---
+
+That’s it. You now have Lyng embedded in your Kotlin app: you can expose your app’s API, evaluate user scripts, and organize your own packages to import from Lyng code.

docs/exceptions_handling.md

@@ -128,15 +128,17 @@ Serializable class that conveys information about the exception. Important membe
 
 | name              | description                                            |
 |-------------------|--------------------------------------------------------|
-| message           | String message                                         |
-| stackTrace        | lyng stack trace, list of `StackTraceEntry`, see below |
-| printStackTrace() | format and print stack trace using println()           |
+| message           | String message                                           |
+| stackTrace()      | lyng stack trace, list of `StackTraceEntry`, see below   |
+| printStackTrace() | format and print stack trace using println()             |
+
+> **Note for Kotlin users**: When working with Lyng exceptions from Kotlin, you can use extension methods like `getLyngExceptionMessageWithStackTrace()`. See [Embedding Lyng](embedding.md#12-handling-and-serializing-exceptions) for the full API.
 
 ## StackTraceEntry
 
 A simple structire that stores single entry in Lyng stack, it is created automatically on exception creation:
 
-```kotlin
+```lyng
 class StackTraceEntry(
     val sourceName: String,
     val line: Int,
@@ -150,22 +152,116 @@ class StackTraceEntry(
 
 # Custom error classes
 
-_this functionality is not yet released_
+You can define your own exception classes by inheriting from the built-in `Exception` class. This allows you to create specific error types for your application logic and catch them specifically.
+
+## Defining a custom exception
+
+To define a custom exception, create a class that inherits from `Exception`:
+
+```lyng
+class MyUserException : Exception("something went wrong")
+```
+
+You can also pass the message dynamically:
+
+```lyng
+class MyUserException(m) : Exception(m)
+
+throw MyUserException("custom error message")
+```
+
+If you don't provide a message to the `Exception` constructor, the class name will be used as the default message:
+
+```lyng
+class SimpleException : Exception
+
+val e = SimpleException()
+assertEquals("SimpleException", e.message)
+```
+
+## Throwing and catching custom exceptions
+
+Custom exceptions are thrown using the `throw` keyword and can be caught using `catch` blocks, just like standard exceptions:
+
+```lyng
+class ValidationException(m) : Exception(m)
+
+try {
+    throw ValidationException("Invalid input")
+}
+catch(e: ValidationException) {
+    println("Caught validation error: " + e.message)
+}
+catch(e: Exception) {
+    println("Caught other exception: " + e.message)
+}
+```
+
+Since user exceptions are real classes, inheritance works as expected:
+
+```lyng
+class BaseError : Exception
+class DerivedError : BaseError
+
+try {
+    throw DerivedError()
+}
+catch(e: BaseError) {
+    // This will catch DerivedError as well
+    assert(e is DerivedError)
+}
+```
+
+## Accessing extra data
+
+You can add your own fields to custom exception classes to carry additional information:
+
+```lyng
+class NetworkException(m, val statusCode) : Exception(m)
+
+try {
+    throw NetworkException("Not Found", 404)
+}
+catch(e: NetworkException) {
+    println("Error " + e.statusCode + ": " + e.message)
+}
+```
 
 # Standard exception classes
 
 | class                      | notes                                                 |
 |----------------------------|-------------------------------------------------------|
-| Exception                  | root of al throwable objects                          |
+| Exception                  | root of all throwable objects                         |
 | NullReferenceException     |                                                       |
 | AssertionFailedException   |                                                       | 
 | ClassCastException         |                                                       |
 | IndexOutOfBoundsException  |                                                       |
 | IllegalArgumentException   |                                                       | 
+| IllegalStateException      |                                                       |
+| NoSuchElementException     |                                                       |
 | IllegalAssignmentException | assigning to val, etc.                                |
 | SymbolNotDefinedException  |                                                       |
 | IterationEndException      | attempt to read iterator past end, `hasNext == false` |
-| AccessException            | attempt to access private members or like             |
-| UnknownException           | unexpected kotlin exception caught                    |
-|                            |                                                       |
+| IllegalAccessException     | attempt to access private members or like             |
+| UnknownException           | unexpected internal exception caught                  |
+| NotFoundException          |                                                       |
+| IllegalOperationException  |                                                       |
+| UnsetException             | access to uninitialized late-init val                 |
+| NotImplementedException    | used by `TODO()`                                      |
+| SyntaxError                |                                                       |
 
+
+### Symbol resolution errors
+
+For compatibility, `SymbolNotFound` is an alias of `SymbolNotDefinedException`. You can catch either name in examples and tests.
+
+Example:
+
+```lyng
+try {
+    nonExistingMethod()
+}
+catch(e: SymbolNotFound) {
+    // handle
+}
+```

docs/fix-scope-parent-cycle.md

@@ -0,0 +1,34 @@
+## Fix: prevent cycles in scope parent chain during pooled frame reuse
+
+### What changed
+- Scope.resetForReuse now fully detaches a reused scope from its previous chain/state before re-parenting:
+  - sets `parent = null` and regenerates `frameId`
+  - clears locals/slots/bindings caches
+  - only after that, validates the new parent with `ensureNoCycle` and assigns it
+- ScopePool.borrow on all targets (JVM, Android, JS, Native, Wasm) now has a defensive fallback:
+  - if `resetForReuse` throws `IllegalStateException` indicating a parent-chain cycle, the pool allocates a fresh `Scope` instead of failing.
+
+### Why
+In some nested call patterns (notably instance method calls where an instance is produced by another function and immediately used), the same pooled `Scope` object can be rebound into a chain that already (transitively) contains it. Reassigning `parent` in that case forms a structural cycle, which `ensureNoCycle` correctly detects and throws. This could surface as:
+
+```
+IllegalStateException: cycle detected in scope parent chain assignment
+  at net.sergeych.lyng.Scope.ensureNoCycle(...)
+  at net.sergeych.lyng.Scope.resetForReuse(...)
+  at net.sergeych.lyng.ScopePool.borrow(...)
+  ... during instance method invocation
+```
+
+The fix removes the failure mode by:
+1) Detaching the reused frame from its prior chain/state before validating and assigning the new parent.
+2) Falling back to a new frame allocation if a cycle is still detected (extremely rare and cheap vs. a crash).
+
+### Expected effects
+- Eliminates sporadic `cycle detected in scope parent chain` crashes during instance method invocation.
+- No change to public API or normal semantics.
+- Pooling remains enabled by default; the fallback only triggers on the detected cycle edge case.
+- Negligible performance impact: fresh allocation is used only when a cycle would have crashed the VM previously.
+
+### Notes
+- The fix is platform-wide (all ScopePool actuals are covered).
+- We recommend adding/keeping a regression test that exercises: a class with a method, a function returning an instance, and an exported function calling the instance method. The test should pass without exceptions.

docs/formatter.md

@@ -0,0 +1,62 @@
+# Lyng formatter (core, CLI, and IDE)
+
+This document describes the Lyng code formatter included in this repository. The formatter lives in the core library (`:lynglib`), is available from the CLI (`lyng fmt`), and is used by the IntelliJ plugin.
+
+## Core library
+
+Package: `net.sergeych.lyng.format`
+
+- `LyngFormatConfig`
+  - `indentSize` (default 4)
+  - `useTabs` (default false)
+  - `continuationIndentSize` (default 8)
+  - `maxLineLength` (default 120)
+  - `applySpacing` (default false)
+  - `applyWrapping` (default false)
+- `LyngFormatter`
+  - `reindent(text, config)` — recomputes indentation from scratch (braces, `else/catch/finally` alignment, continuation indent under `(` `)` and `[` `]`), idempotent.
+  - `format(text, config)` — runs `reindent` and, depending on `config`, optionally applies:
+    - a safe spacing pass (commas/operators/colons/keyword parens; member access `.` remains tight; no changes to strings/comments), and
+    - a controlled wrapping pass for long call arguments (no trailing commas).
+
+Both passes are designed to be idempotent. Extensive tests live under `:lynglib/src/commonTest/.../format`.
+
+## CLI formatter
+
+```
+lyng fmt [--check] [--in-place|-i] [--spacing] [--wrap] <file1.lyng> [file2.lyng ...]
+```
+
+- Defaults: indent-only; spacing and wrapping are OFF unless flags are provided.
+- `--check` prints files that would change and exits with code 2 if any changes are detected.
+- `--in-place`/`-i` rewrites files in place (default if not using `--check`).
+- `--spacing` enables the safe spacing pass (commas/operators/colons/keyword parens).
+- `--wrap` enables controlled wrapping of long call argument lists (respects `maxLineLength`, no trailing commas).
+
+Examples:
+
+```
+# check formatting without modifying files
+lyng fmt --check docs/samples/fs_sample.lyng
+
+# format in place with spacing rules enabled
+lyng fmt --spacing -i docs/samples/fs_sample.lyng
+
+# format in place with spacing + wrapping
+lyng fmt --spacing --wrap -i src/**/*.lyng
+```
+
+## IntelliJ plugin
+
+- Indentation: always enabled, idempotent; the plugin computes per-line indent via the core formatter.
+- Spacing/wrapping: optional and OFF by default.
+  - Settings/Preferences → Lyng Formatter provides toggles:
+    - "Enable spacing normalization (commas/operators/colons/keyword parens)"
+    - "Enable line wrapping (120 cols) [experimental]"
+  - Reformat Code applies: indentation first, then spacing, then wrapping if toggled.
+
+## Design notes
+
+- Single source of truth: The core formatter is used by CLI and IDE to keep behavior consistent.
+- Stability first: Spacing/wrapping are gated by flags/toggles; indentation from scratch is always safe and idempotent.
+- Non-destructive: The formatter carefully avoids changing string/char literals and comment contents.

docs/generics.md

@@ -0,0 +1,146 @@
+# Generics and type expressions
+
+This document covers generics, bounds, unions/intersections, and the rules for type expressions in Lyng.
+
+# Generic parameters
+
+Declare type parameters with `<...>` on functions and classes:
+
+    fun id<T>(x: T): T = x
+    class Box<T>(val value: T)
+
+Type arguments are usually inferred at call sites:
+
+    val b = Box(10)     // Box<Int>
+    val s = id("ok")    // T is String
+
+# Bounds
+
+Use `:` to set bounds. Bounds may be unions (`|`) or intersections (`&`):
+
+    fun sum<T: Int | Real>(x: T, y: T) = x + y
+    class Named<T: Iterable & Comparable>(val data: T)
+
+Bounds are checked at compile time. For union bounds, the argument must fit at least one option. For intersection bounds, it must fit all options.
+
+# Variance
+
+Generic types are invariant by default. You can specify declaration-site variance:
+
+    class Source<out T>(val value: T)
+    class Sink<in T> { fun accept(x: T) { ... } }
+
+`out` makes the type covariant (produced), `in` makes it contravariant (consumed).
+
+# Type aliases
+
+Type aliases name type expressions (including unions/intersections):
+
+    type Num = Int | Real
+    type AB = A & B
+
+Aliases can be generic and can use bounds and defaults:
+
+    type Maybe<T> = T?
+    type IntList<T: Int> = List<T>
+
+Aliases expand to their underlying type expressions. They can be used anywhere a type expression is expected.
+
+# Inference rules
+
+- Literals set obvious types (`1` is `Int`, `1.0` is `Real`, etc.).
+- Empty list literals default to `List<Object>` unless constrained by context.
+- Non-empty list literals infer element type as a union of element types.
+- Map literals infer key and value types; named keys are `String`.
+
+Examples:
+
+    val a = [1, 2, 3]             // List<Int>
+    val b = [1, "two", true]      // List<Int | String | Bool>
+    val c: List<Int> = []         // List<Int>
+
+    val m1 = { "a": 1, "b": 2 }   // Map<String, Int>
+    val m2 = { "a": 1, "b": "x" } // Map<String, Int | String>
+    val m3 = { ...m1, "c": true } // Map<String, Int | Bool>
+
+Map spreads carry key/value types when possible.
+
+Spreads propagate element type when possible:
+
+    val base = [1, 2]
+    val mix = [...base, 3]        // List<Int>
+
+# Type expressions
+
+Type expressions include simple types, generics, unions, and intersections:
+
+    Int
+    List<String>
+    Int | String
+    Iterable & Comparable
+
+These type expressions can appear in casts and `is` checks.
+
+# `is`, `in`, and `==` with type expressions
+
+There are two categories of `is` checks:
+
+1) Value checks: `x is T`
+   - `x` is a value, `T` is a type expression.
+   - This is a runtime instance check.
+
+2) Type checks: `T1 is T2`
+   - both sides are type expressions (class objects or unions/intersections).
+   - This is a *type-subset* check: every value of `T1` must fit in `T2`.
+
+Exact type expression equality uses `==` and is structural (union/intersection order does not matter).
+
+Includes checks use `in` with type expressions:
+
+    A in T
+
+This means `A` is a subset of `T` (the same relation as `A is T`).
+
+Examples (T = A | B):
+
+    T == A            // false
+    T is A            // false
+    A in T            // true
+    B in T            // true
+    T is A | B        // true
+
+# Nullability checks for types
+
+Use `is nullable` to check whether a type expression accepts `null`:
+
+    T is nullable
+    T !is nullable
+
+This works with concrete and generic types:
+
+    fun describe<T>(x: T): String = when (T) {
+        nullable -> "nullable"
+        else -> "non-null"
+    }
+
+Equivalent legacy form:
+
+    null is T
+
+# Practical examples
+
+    fun acceptInts<T: Int>(xs: List<T>) { }
+    acceptInts([1, 2, 3])
+    // acceptInts([1, "a"]) -> compile-time error
+
+    fun f<T>(list: List<T>) {
+        assert( T is Int | String | Bool )
+        assert( !(T is Int) )
+        assert( Int in T )
+    }
+    f([1, "two", true])
+
+# Notes
+
+- `T` is reified as a type expression when needed (e.g., union/intersection). When it is a single class, `T` is that class object.
+- Type expression checks are compile-time where possible; runtime checks only happen for `is` on values and explicit casts.

docs/idea_plugin.md

@@ -0,0 +1,32 @@
+# Plugin for IntelliJ IDEA
+
+[//]: # (excludeFromIndex)
+
+We introduce the alpha version of the plugin for IntelliJ IDEA 2024.3.x+ IDE variants. It is compatible with 2025.x and
+should be compatible with other IDEA flavors, notably [OpenIDE](https://openide.ru/). It supports the following features:
+
+- syntax highlighting (2 stage, fast and more accurate that analyses in background)
+- reformat code (indents, spaces)
+- reformat on paste
+- smart enter key
+- `.lyng.d` definition files (merged into analysis for completion, navigation, Quick Docs, and error checking)
+
+Features are configurable via the plugin settings page, in system settings.
+
+See `docs/lyng_d_files.md` for `.lyng.d` syntax and examples.
+
+> Recommended for IntelliJ-based IDEs: While IntelliJ can import TextMate bundles
+> (Settings/Preferences → Editor → TextMate Bundles), the native Lyng plugin provides
+> better support (formatting, smart enter, background analysis, etc.). Prefer installing
+> this plugin over using a TextMate bundle.
+
+### Install
+
+- From ZIP: download the archive below, then in IntelliJ IDEA open Settings/Preferences → Plugins →
+  gear icon → Install Plugin from Disk… and select the downloaded ZIP. Restart IDE if prompted.
+- Alternatively, if/when the plugin is published to a marketplace, you will be able to install it
+  directly from the “Marketplace” tab (not yet available).
+
+### [Download plugin v0.0.2-SNAPSHOT](https://lynglang.com/distributables/lyng-idea-0.0.2-SNAPSHOT.zip)
+
+Your ideas and bugreports are welcome on the [project gitea page](https://gitea.sergeych.net/SergeychWorks/lyng/issues)

docs/json_and_kotlin_serialization.md

@@ -0,0 +1,178 @@
+# Json support
+
+Since 1.0.5 we start adding JSON support. Versions 1,0,6* support serialization of the basic types, including lists and
+maps, and simple classes. Multiple inheritance may produce incorrect results, it is work in progress.
+
+## Serialization in Lyng
+
+    // in lyng
+    assertEquals("{\"a\":1}", {a: 1}.toJsonString())
+    void
+    >>> void
+
+Simple classes serialization is supported:
+
+    import lyng.serialization
+    class Point(foo,bar) {
+        val t = 42
+    }
+    // val is not serialized
+    assertEquals( "{\"foo\":1,\"bar\":2}", Point(1,2).toJsonString() )
+    >>> void
+
+Note that mutable members are serialized by default. You can exclude any member (including constructor parameters) from JSON serialization using the `@Transient` attribute:
+
+    import lyng.serialization
+    
+    class Point2(@Transient val foo, val bar) {
+        @Transient var reason = 42
+        var visible = 100
+    }
+    assertEquals( "{\"bar\":2,\"visible\":100}", Point2(1,2).toJsonString() )
+    >>> void
+
+Note that if you override json serialization:
+
+    import lyng.serialization
+    
+    class Point2(foo,bar) {
+        var reason = 42
+        // but we override json serialization:
+        fun toJsonObject() {
+            { "custom": true }
+        }
+    }
+    // var is serialized instead
+    assertEquals( "{\"custom\":true}", Point2(1,2).toJsonString() )
+    >>> void
+
+Custom serialization of user classes is possible by overriding `toJsonObject` method. It must return an object which is
+serializable to Json. Most often it is a map, but any object is accepted, that makes it very flexible:
+
+    import lyng.serialization
+    
+    class Point2(foo,bar) {
+        var reason = 42
+        // but we override json serialization:
+        fun toJsonObject() {
+            { "custom": true }
+        }
+    }
+    class Custom {
+        fun toJsonObject() {
+            "full freedom"
+        }
+    }
+    // var is serialized instead
+    assertEquals( "\"full freedom\"", Custom().toJsonString() )
+    >>> void
+
+Please note that `toJsonString` should be used to get serialized string representation of the object. Don't call
+`toJsonObject` directly, it is not intended to be used outside the serialization library.
+
+## Kotlin side interfaces
+
+The "Batteries included" principle is also applied to serialization.
+
+- `Obj.toJson()` provides Kotlin `JsonElement`
+- `Obj.toJsonString()` provides Json string representation
+- `Obj.decodeSerializableWith()` and `Obj.decodeSerializable()` allows to decode Lyng classes as Kotlin objects using
+  `kotlinx.serialization`:
+
+```kotlin
+/**
+ * Decodes the current object into a deserialized form using the provided deserialization strategy.
+ * It is based on [Obj.toJson] and uses existing Kotlin Json serialization, without string representation
+ * (only `JsonElement` to carry information between Kotlin and Lyng serialization worlds), thus efficient.
+ *
+ * @param strategy The deserialization strategy that defines how the object should be decoded.
+ * @param scope An optional scope used during deserialization to define the context. Defaults to a new instance of Scope.
+ * @return The deserialized object of type T.
+ */
+suspend fun <T> Obj.decodeSerializableWith(strategy: DeserializationStrategy<T>, scope: Scope = Scope()): T =
+    Json.decodeFromJsonElement(strategy, toJson(scope))
+
+/**
+ * Decodes a serializable object of type [T] using the provided decoding scope. The deserialization uses
+ * [Obj.toJson] and existing Json based serialization ithout using actual string representation, thus
+ * efficient.
+ *
+ * @param T The type of the object to be decoded. Must be a reified type.
+ * @param scope The scope used during decoding. Defaults to a new instance of [Scope].
+ */
+suspend inline fun <reified T> Obj.decodeSerializable(scope: Scope = Scope()) =
+    decodeSerializableWith<T>(serializer<T>(), scope)
+```
+
+Note that lyng-2-kotlin deserialization with `kotlinx.serialization` uses JsonElement as information carrier without
+formatting and parsing actual Json strings. This is why we use `Json.decodeFromJsonElement` instead of
+`Json.decodeFromString`. Such an approach gives satisfactory performance without writing and supporting custom
+`kotlinx.serialization` codecs.
+
+### Pitfall: JSON objects and Map<String, Any?>
+
+Kotlin serialization does not support `Map<String, Any?>` as a serializable type, more general, it can't serialize `Any`. This in particular means that you can deserialize Kotlin `Map<String, T>` as long as `T` is `@Serializable` in Kotlin: 
+
+```kotlin
+@Serializable
+data class TestJson2(
+    val value: Int,
+    val inner: Map<String,Int>
+)
+
+@Test
+fun deserializeMapWithJsonTest() = runTest {
+    val x = eval("""
+        import lyng.serialization
+        { value: 1, inner: { "foo": 1, "bar": 2 }}
+    """.trimIndent()).decodeSerializable<TestJson2>()
+    // That works perfectly well:
+    assertEquals(TestJson2(1, mapOf("foo" to 1, "bar" to 2)), x)
+}
+```
+
+But what if your map has objects of different types? The approach of using polymorphism is partially applicable, but what to do with `{ one: 1, two: "two" }`?
+
+The answer is pretty simple: use `JsonObject` in your deserializable object. This class is capable of holding any JSON types and structures and is sort of a silver bullet for such cases:
+
+~~~kotlin
+@Serializable
+data class TestJson3(
+    val value: Int,
+    val inner: JsonObject
+)
+@Test
+fun deserializeAnyMapWithJsonTest() = runTest {
+    val x = eval("""
+        import lyng.serialization
+        { value: 12, inner: { "foo": 1, "bar": "two" }}
+    """.trimIndent()).decodeSerializable<TestJson3>()
+    assertEquals(TestJson3(12, JsonObject(mapOf("foo" to JsonPrimitive(1), "bar" to Json.encodeToJsonElement("two")))), x)
+}
+~~~
+
+
+# List of supported types
+
+| Lyng type | JSON type | notes       |
+|-----------|-----------|-------------|
+| `Int`     | number    |             |
+| `Real`    | number    |             |
+| `String`  | string    |             |
+| `Bool`    | boolean   |             |
+| `null`    | null      |             |
+| `Instant` | string    | ISO8601 (1) |
+| `List`    | array     | (2)         |
+| `Map`     | object    | (2)         |
+
+
+(1)
+: ISO8601 flavor 1970-05-06T06:00:00.000Z in used; number of fractional digits depends on the truncation
+on [Instant](time.md), see `Instant.truncateTo...` functions.
+
+(2)
+: List may contain any objects serializable to Json.
+
+(3)
+: Map keys must be strings, map values may be any objects serializable to Json.
+

docs/lyng.io.console.md

@@ -0,0 +1,101 @@
+### lyng.io.console
+
+`lyng.io.console` provides optional rich console support for terminal applications.
+
+> **Note:** this module is part of `lyngio`. It must be explicitly installed into the import manager by host code.
+>
+> **CLI note:** the `lyng` CLI now installs `lyng.io.console` in its base scope by default, so scripts can simply `import lyng.io.console`.
+
+#### Install in host
+
+```kotlin
+import net.sergeych.lyng.Script
+import net.sergeych.lyng.io.console.createConsoleModule
+import net.sergeych.lyngio.console.security.PermitAllConsoleAccessPolicy
+
+suspend fun initScope() {
+    val scope = Script.newScope()
+    createConsoleModule(PermitAllConsoleAccessPolicy, scope)
+}
+```
+
+#### Use in Lyng script
+
+```lyng
+import lyng.io.console
+
+println("supported = " + Console.isSupported())
+println("tty = " + Console.isTty())
+println("ansi = " + Console.ansiLevel())
+println("geometry = " + Console.geometry())
+
+Console.write("hello\n")
+Console.home()
+Console.clear()
+Console.moveTo(1, 1)
+Console.clearLine()
+Console.enterAltScreen()
+Console.leaveAltScreen()
+Console.setCursorVisible(true)
+Console.flush()
+```
+
+Interactive sample script in this repo:
+
+```bash
+lyng examples/tetris_console.lyng
+```
+
+#### API
+
+- `Console.isSupported(): Bool` — whether console control is available on this platform/runtime.
+- `Console.isTty(): Bool` — whether output is attached to a TTY.
+- `Console.ansiLevel(): String` — `NONE`, `BASIC16`, `ANSI256`, `TRUECOLOR`.
+- `Console.geometry(): ConsoleGeometry?` — `{columns, rows}` as typed object or `null`.
+- `Console.details(): ConsoleDetails` — consolidated capability object.
+- `Console.write(text: String)` — writes to console output.
+- `Console.flush()` — flushes buffered output.
+- `Console.home()` — moves cursor to top-left.
+- `Console.clear()` — clears visible screen.
+- `Console.moveTo(row: Int, column: Int)` — moves cursor to 1-based row/column.
+- `Console.clearLine()` — clears current line.
+- `Console.enterAltScreen()` — switch to alternate screen buffer.
+- `Console.leaveAltScreen()` — return to normal screen buffer.
+- `Console.setCursorVisible(visible: Bool)` — shows/hides cursor.
+- `Console.events(): ConsoleEventStream` — endless iterable source of typed events: `ConsoleResizeEvent`, `ConsoleKeyEvent`.
+- `Console.setRawMode(enabled: Bool): Bool` — requests raw input mode, returns `true` if changed.
+
+#### Event Iteration
+
+Use events from a loop, typically in a separate coroutine:
+
+```lyng
+launch {
+    for (ev in Console.events()) {
+        if (ev is ConsoleKeyEvent) {
+            // handle key
+        }
+    }
+}
+```
+
+#### Event format
+
+`Console.events()` emits `ConsoleEvent` with at least:
+
+- `type: String` — `resize`, `keydown`, `keyup`
+
+Additional fields:
+
+- `ConsoleResizeEvent`: `columns`, `rows`
+- `ConsoleKeyEvent`: `key`, `code`, `ctrl`, `alt`, `shift`, `meta`
+
+#### Security policy
+
+The module uses `ConsoleAccessPolicy` with operations:
+
+- `WriteText(length)`
+- `ReadEvents`
+- `SetRawMode(enabled)`
+
+For permissive mode, use `PermitAllConsoleAccessPolicy`.

docs/lyng.io.fs.md

@@ -0,0 +1,232 @@
+### lyng.io.fs — async filesystem access for Lyng scripts
+
+This module provides a uniform, suspend-first filesystem API to Lyng scripts, backed by Kotlin Multiplatform implementations.
+
+- JVM/Android/Native: Okio `FileSystem.SYSTEM` (non-blocking via coroutine dispatcher)
+- JS/Node: Node filesystem (currently via Okio node backend; a native `fs/promises` backend is planned)
+- JS/Browser and Wasm: in-memory virtual filesystem for now
+
+It exposes a Lyng class `Path` with methods for file and directory operations, including streaming readers for large files.
+
+It is a separate library because access to the filesystem is a security risk we compensate with a separate API that user must explicitly include to the dependency and allow. Together with `FsAccessPolicy` that is required to `createFs()` which actually adds the filesystem to the scope, the security risk is isolated.
+
+Also, it helps keep Lyng core small and focused.
+
+---
+
+#### Add the library to your project (Gradle)
+
+If you use this repository as a multi-module project, add a dependency on `:lyngio`:
+
+```kotlin
+dependencies {
+    implementation("net.sergeych:lyngio:0.0.1-SNAPSHOT")
+}
+```
+Note on maven repository. Lyngio uses the same maven as Lyng code (`lynglib`) so it is most likely already in your project. If not, add it to the proper section of your `build.gradle.kts` or settings.gradle.kts:
+
+```kotlin
+    repositories {
+        maven("https://gitea.sergeych.net/api/packages/SergeychWorks/maven")
+    }
+```
+
+This brings in:
+
+- `:lynglib` (Lyng engine)
+- Okio (`okio`, `okio-fakefilesystem`, and `okio-nodefilesystem` for JS)
+- Kotlin coroutines
+
+---
+
+#### Install the module into a Lyng Scope
+
+The filesystem module is not installed automatically. You must explicitly register it in the scope’s `ImportManager` using the installer. You can customize access control via `FsAccessPolicy`.
+
+Kotlin (host) bootstrap example:
+
+```kotlin
+import net.sergeych.lyng.Scope
+import net.sergeych.lyng.io.fs.createFs
+import net.sergeych.lyngio.fs.security.PermitAllAccessPolicy
+
+val scope: Scope = Scope.new()
+val installed: Boolean = createFs(PermitAllAccessPolicy, scope)
+// installed == true on first registration in this ImportManager, false on repeats
+
+// In scripts (or via scope.eval), import the module to use its symbols:
+scope.eval("import lyng.io.fs")
+```
+
+You can install with a custom policy too (see Access policy below).
+
+---
+
+#### Using from Lyng scripts
+
+```lyng
+val p = Path("/tmp/hello.txt")
+
+// Text I/O
+p.writeUtf8("Hello Lyng!\n")
+println(p.readUtf8())
+
+// Binary I/O
+val data = Buffer.fromHex("deadbeef")
+p.writeBytes(data)
+
+// Existence and directories
+assertTrue(p.exists())
+Path("/tmp/work").mkdirs()
+
+// Listing
+for (entry in Path("/tmp").list()) {
+    println(entry)
+}
+
+// Globbing
+val txts = Path("/tmp").glob("**/*.txt").toList()
+
+// Copy / Move / Delete
+Path("/tmp/a.txt").copy("/tmp/b.txt", overwrite=true)
+Path("/tmp/b.txt").move("/tmp/c.txt", overwrite=true)
+Path("/tmp/c.txt").delete()
+
+// Streaming large files (does not load whole file into memory)
+var bytes = 0
+val it = Path("/tmp/big.bin").readChunks(1_048_576) // 1MB chunks
+val iter = it.iterator()
+while (iter.hasNext()) {
+    val chunk = iter.next()
+    bytes = bytes + chunk.size()
+}
+
+// Text chunks and lines
+for (s in Path("/tmp/big.txt").readUtf8Chunks(64_000)) {
+    // process each string chunk
+}
+
+for (ln in Path("/tmp/big.txt").lines()) {
+    // process line by line
+}
+```
+
+---
+
+#### API (Lyng class `Path`)
+
+Constructor:
+- `Path(path: String)` — creates a Path object
+- `Paths(path: String)` — alias
+
+File and directory operations (all suspend under the hood):
+- `name`: name, `String`
+- `segments`: list of parsed path segments (directories)
+- `parent`: parent directory, `Path?`; null if root
+- `exists(): Bool`
+- `isFile(): Bool` — true if the path points to a regular file (cached metadata)
+- `isDirectory(): Bool` — true if the path points to a directory (cached metadata)
+- `size(): Int?` — size in bytes or null if unknown (cached metadata)
+- `createdAt(): Instant?` — creation time as Lyng `Instant`, or null (cached metadata)
+- `createdAtMillis(): Int?` — creation time in epoch milliseconds, or null (cached metadata)
+- `modifiedAt(): Instant?` — last modification time as Lyng `Instant`, or null (cached metadata)
+- `modifiedAtMillis(): Int?` — last modification time in epoch milliseconds, or null (cached metadata)
+- `list(): List<Path>` — children of a directory
+- `readBytes(): Buffer`
+- `writeBytes(bytes: Buffer)`
+- `appendBytes(bytes: Buffer)`
+- `readUtf8(): String`
+- `writeUtf8(text: String)`
+- `appendUtf8(text: String)`
+- `metadata(): Map` — keys: `isFile`, `isDirectory`, `size`, `createdAtMillis`, `modifiedAtMillis`, `isSymlink`
+- `mkdirs(mustCreate: Bool = false)`
+- `move(to: Path|String, overwrite: Bool = false)`
+- `delete(mustExist: Bool = false, recursively: Bool = false)`
+- `copy(to: Path|String, overwrite: Bool = false)`
+- `glob(pattern: String): List<Path>` — supports `**`, `*`, `?` (POSIX-style)
+
+Streaming readers for big files:
+- `readChunks(size: Int = 65536): Iterator<Buffer>` — iterate fixed-size byte chunks
+- `readUtf8Chunks(size: Int = 65536): Iterator<String>` — iterate text chunks by character count
+- `lines(): Iterator<String>` — line iterator built on `readUtf8Chunks`
+
+Notes:
+- Iterators implement Lyng iterator protocol. If you break early from a loop, the runtime will attempt to call `cancelIteration()` when available.
+- Current implementations chunk in memory. The public API is stable; internals will evolve to true streaming on all platforms.
+- Attribute accessors (`isFile`, `isDirectory`, `size`, `createdAt*`, `modifiedAt*`) cache a metadata snapshot inside the `Path` instance to avoid repeated filesystem calls during a sequence of queries. `metadata()` remains available for bulk access.
+
+---
+
+#### Access policy (security)
+
+Access control is enforced by `FsAccessPolicy`. You pass a policy at installation time. The module wraps the filesystem with a secured decorator that consults the policy for each primitive operation.
+
+Main types:
+- `FsAccessPolicy` — your policy implementation
+- `PermitAllAccessPolicy` — allows all operations (default for testing)
+- `AccessOp` (sealed) — operations the policy can decide on:
+  - `ListDir(path)`
+  - `CreateFile(path)`
+  - `OpenRead(path)`
+  - `OpenWrite(path)`
+  - `OpenAppend(path)`
+  - `Delete(path)`
+  - `Rename(from, to)`
+  - `UpdateAttributes(path)` — defaults to write-level semantics
+
+Minimal denying policy example (imports omitted for brevity):
+
+```kotlin
+val denyWrites = object : FsAccessPolicy {
+    override suspend fun check(op: AccessOp, ctx: AccessContext): AccessDecision = when (op) {
+        is AccessOp.OpenRead, is AccessOp.ListDir -> AccessDecision(Decision.Allow)
+        else -> AccessDecision(Decision.Deny, reason = "read-only policy")
+    }
+}
+
+createFs(denyWrites, scope)
+scope.eval("import lyng.io.fs")
+```
+
+Composite operations like `copy` and `move` are checked as a set of primitives (e.g., `OpenRead(src)` + `Delete(dst)` if overwriting + `CreateFile(dst)` + `OpenWrite(dst)`).
+
+---
+
+#### Errors and exceptions
+
+Policy denials are surfaced as Lyng runtime errors, not raw Kotlin exceptions:
+- Internally, a denial throws `AccessDeniedException`. The module maps it to `ObjIllegalOperationException` wrapped into an `ExecutionError` visible to scripts.
+
+Examples (Lyng):
+
+```lyng
+import lyng.io.fs
+val p = Path("/protected/file.txt")
+try {
+    p.writeUtf8("x")
+    fail("expected error")
+} catch (e) {
+    // e is an ExecutionError; message contains the policy reason
+}
+```
+
+Other I/O failures (e.g., not found, not a directory) are also raised as Lyng errors (`ObjIllegalStateException`, `ObjIllegalArgumentException`, etc.) depending on context.
+
+---
+
+#### Platform notes
+
+- JVM/Android/Native: synchronous Okio calls are executed on `Dispatchers.IO` (JVM/Android) or `Dispatchers.Default` (Native) to avoid blocking the main thread.
+- NodeJS: currently uses Okio’s Node backend. For heavy I/O, a native `fs/promises` backend is planned to fully avoid event-loop blocking.
+- Browser/Wasm: uses an in-memory filesystem for now. Persistent backends (IndexedDB or File System Access API) are planned.
+
+---
+
+#### Roadmap
+
+- Native NodeJS backend using `fs/promises`
+- Browser persistent storage (IndexedDB)
+- Streaming readers/writers over real OS streams
+- Attribute setters and richer metadata
+
+If you have specific needs (e.g., sandboxing, virtual roots), implement a custom `FsAccessPolicy` or ask us to add a helper.

docs/lyng.io.process.md

@@ -0,0 +1,136 @@
+### lyng.io.process — Process execution and control for Lyng scripts
+
+This module provides a way to run external processes and shell commands from Lyng scripts. It is designed to be multiplatform and uses coroutines for non-blocking execution.
+
+> **Note:** `lyngio` is a separate library module. It must be explicitly added as a dependency to your host application and initialized in your Lyng scopes.
+
+---
+
+#### Add the library to your project (Gradle)
+
+If you use this repository as a multi-module project, add a dependency on `:lyngio`:
+
+```kotlin
+dependencies {
+    implementation("net.sergeych:lyngio:0.0.1-SNAPSHOT")
+}
+```
+
+For external projects, ensure you have the appropriate Maven repository configured (see `lyng.io.fs` documentation).
+
+---
+
+#### Install the module into a Lyng Scope
+
+The process module is not installed automatically. You must explicitly register it in the scope’s `ImportManager` using `createProcessModule`. You can customize access control via `ProcessAccessPolicy`.
+
+Kotlin (host) bootstrap example:
+
+```kotlin
+import net.sergeych.lyng.Scope
+import net.sergeych.lyng.Script
+import net.sergeych.lyng.io.process.createProcessModule
+import net.sergeych.lyngio.process.security.PermitAllProcessAccessPolicy
+
+// ... inside a suspend function or runBlocking
+val scope: Scope = Script.newScope()
+createProcessModule(PermitAllProcessAccessPolicy, scope)
+
+// In scripts (or via scope.eval), import the module:
+scope.eval("import lyng.io.process")
+```
+
+---
+
+#### Using from Lyng scripts
+
+```lyng
+import lyng.io.process
+
+// Execute a process with arguments
+val p = Process.execute("ls", ["-l", "/tmp"])
+for (line in p.stdout) {
+    println("OUT: " + line)
+}
+val exitCode = p.waitFor()
+println("Process exited with: " + exitCode)
+
+// Run a shell command
+val sh = Process.shell("echo 'Hello from shell' | wc -w")
+for (line in sh.stdout) {
+    println("Word count: " + line.trim())
+}
+
+// Platform information
+val details = Platform.details()
+println("OS: " + details.name + " " + details.version + " (" + details.arch + ")")
+if (details.kernelVersion != null) {
+    println("Kernel: " + details.kernelVersion)
+}
+
+if (Platform.isSupported()) {
+    println("Processes are supported!")
+}
+```
+
+---
+
+#### API Reference
+
+##### `Process` (static methods)
+- `execute(executable: String, args: List<String>): RunningProcess` — Start an external process.
+- `shell(command: String): RunningProcess` — Run a command through the system shell (e.g., `/bin/sh` or `cmd.exe`).
+
+##### `RunningProcess` (instance methods)
+- `stdout: Flow` — Standard output stream as a Lyng Flow of lines.
+- `stderr: Flow` — Standard error stream as a Lyng Flow of lines.
+- `waitFor(): Int` — Wait for the process to exit and return the exit code.
+- `signal(name: String)` — Send a signal to the process (e.g., `"SIGINT"`, `"SIGTERM"`, `"SIGKILL"`).
+- `destroy()` — Forcefully terminate the process.
+
+##### `Platform` (static methods)
+- `details(): Map` — Get platform details. Returned map keys: `name`, `version`, `arch`, `kernelVersion`.
+- `isSupported(): Bool` — True if process execution is supported on the current platform.
+
+---
+
+#### Security Policy
+
+Process execution is a sensitive operation. `lyngio` uses `ProcessAccessPolicy` to control access to `execute` and `shell` operations.
+
+- `ProcessAccessPolicy` — Interface for custom policies.
+- `PermitAllProcessAccessPolicy` — Allows all operations.
+- `ProcessAccessOp` (sealed) — Operations to check:
+    - `Execute(executable, args)`
+    - `Shell(command)`
+
+Example of a restricted policy in Kotlin:
+
+```kotlin
+import net.sergeych.lyngio.fs.security.AccessDecision
+import net.sergeych.lyngio.fs.security.Decision
+import net.sergeych.lyngio.process.security.ProcessAccessOp
+import net.sergeych.lyngio.process.security.ProcessAccessPolicy
+
+val restrictedPolicy = object : ProcessAccessPolicy {
+    override suspend fun check(op: ProcessAccessOp, ctx: AccessContext): AccessDecision {
+        return when (op) {
+            is ProcessAccessOp.Execute -> {
+                if (op.executable == "ls") AccessDecision(Decision.Allow)
+                else AccessDecision(Decision.Deny, "Only 'ls' is allowed")
+            }
+            is ProcessAccessOp.Shell -> AccessDecision(Decision.Deny, "Shell is forbidden")
+        }
+    }
+}
+createProcessModule(restrictedPolicy, scope)
+```
+
+---
+
+#### Platform Support
+
+- **JVM:** Full support using `ProcessBuilder`.
+- **Native (Linux/macOS):** Support via POSIX.
+- **Windows:** Support planned.
+- **Android/JS/iOS/Wasm:** Currently not supported; `isSupported()` returns `false` and attempts to run processes will throw `UnsupportedOperationException`.

docs/lyng_cli.md

@@ -0,0 +1,141 @@
+### Lyng CLI (`lyng`)
+
+The Lyng CLI is the reference command-line tool for the Lyng language. It lets you:
+
+- Run Lyng scripts from files or inline strings (shebangs accepted)
+- Use standard argument passing (`ARGV`) to your scripts.
+- Format Lyng source files via the built-in `fmt` subcommand.
+
+
+#### Building on Linux
+
+Requirements:
+- JDK 17+ (for Gradle and the JVM distribution)
+- GNU zip utilities (for packaging the native executable)
+- upx tool (executable in-place compression)
+
+The repository provides convenience scripts in `bin/` for local builds and installation into `~/bin`.
+
+Note: In this repository the scripts are named `bin/local_release` and `bin/local_jrelease`. In some environments these may be aliased as `bin/release` and `bin/jrelease`. The steps below use the actual file names present here.
+
+
+##### Option A: Native linuxX64 executable (`lyng`)
+
+1) Build the native binary:
+
+```
+./gradlew :lyng:linkReleaseExecutableLinuxX64
+```
+
+2) Install and package locally:
+
+```
+bin/local_release
+```
+
+What this does:
+- Copies the built executable to `~/bin/lyng` for easy use in your shell.
+- Produces `distributables/lyng-linuxX64.zip` containing the `lyng` executable.
+
+
+##### Option B: JVM distribution (`jlyng` launcher)
+
+This creates a JVM distribution with a launcher script and links it to `~/bin/jlyng`.
+
+```
+bin/local_jrelease
+```
+
+What this does:
+- Runs `./gradlew :lyng:installJvmDist` to build the JVM app distribution to `lyng/build/install/lyng-jvm`.
+- Copies the distribution under `~/bin/jlyng-jvm`.
+- Creates a symlink `~/bin/jlyng` pointing to the launcher script.
+
+
+#### Usage
+
+Once installed, ensure `~/bin` is on your `PATH`. You can then use either the native `lyng` or the JVM `jlyng` launcher (both have the same CLI surface).
+
+
+##### Running scripts
+
+- Run a script by file name and pass arguments to `ARGV`:
+
+```
+lyng path/to/script.lyng arg1 arg2
+```
+
+- Run a script whose name starts with `-` using `--` to stop option parsing:
+
+```
+lyng -- -my-script.lyng arg1 arg2
+```
+
+- Execute inline code with `-x/--execute` and pass positional args to `ARGV`:
+
+```
+lyng -x "println(\"Hello\")" more args
+```
+
+- Print version/help:
+
+```
+lyng --version
+lyng --help
+```
+
+### Use in shell scripts
+
+Standard unix shebangs (`#!`) are supported, so you can make Lyng scripts directly executable on Unix-like systems. For example:
+
+    #!/usr/bin/env lyng
+    println("Hello, world!")
+
+
+##### Formatting source: `fmt` subcommand
+
+Format Lyng files with the built-in formatter.
+
+Basic usage:
+
+```
+lyng fmt [OPTIONS] FILE...
+```
+
+Options:
+- `--check` — Check-only mode. Prints file paths that would change and exits with code 2 if any changes are needed, 0 otherwise.
+- `-i, --in-place` — Write formatted content back to the source files (off by default).
+- `--spacing` — Apply spacing normalization.
+- `--wrap`, `--wrapping` — Enable line wrapping.
+
+Semantics and exit codes:
+- Default behavior is to write formatted content to stdout. When multiple files are provided, the output is separated with `--- <path> ---` headers.
+- `--check` and `--in-place` are mutually exclusive; using both results in an error and exit code 1.
+- `--check` exits with 2 if any file would change, with 0 otherwise.
+- Other errors (e.g., I/O issues) result in a non-zero exit code.
+
+Examples:
+
+```
+# Print formatted content to stdout
+lyng fmt src/file.lyng
+
+# Format multiple files to stdout with headers
+lyng fmt src/a.lyng src/b.lyng
+
+# Check mode: list files that would change; exit 2 if changes are needed
+lyng fmt --check src/**/*.lyng
+
+# In-place formatting
+lyng fmt -i src/**/*.lyng
+
+# Enable spacing normalization and wrapping
+lyng fmt --spacing --wrap src/file.lyng
+```
+
+
+#### Notes
+
+- Both native and JVM distributions expose the same CLI interface. Use whichever best fits your environment.
+- When executing scripts, all positional arguments after the script name are available in Lyng as `ARGV`.
+- The interpreter recognizes shebang lines (`#!`) at the beginning of a script file and ignores them at runtime, so you can make Lyng scripts directly executable on Unix-like systems.

docs/lyng_d_files.md

@@ -0,0 +1,116 @@
+# `.lyng.d` Definition Files
+
+`.lyng.d` files declare Lyng symbols for tooling without shipping runtime implementations. The IntelliJ IDEA plugin merges
+all `*.lyng.d` files from the current directory and its parent directories into the active file’s analysis, enabling:
+
+- completion
+- navigation
+- error checking for declared symbols
+- Quick Docs for declarations defined in `.lyng.d`
+
+Place `*.lyng.d` files next to the code they describe (or in a parent folder). The plugin will pick them up automatically.
+
+## Writing `.lyng.d` Files
+
+You can declare any language-level symbol in a `.lyng.d` file. Use doc comments before declarations to make Quick Docs
+work in the IDE. The doc parser accepts standard comments (`/** ... */` or `// ...`) and supports tags like `@param`.
+
+### Full Example
+
+```lyng
+/** Library entry point */
+extern fun connect(url: String, timeoutMs: Int = 5000): Client
+
+/** Type alias with generics */
+type NameMap = Map<String, String>
+
+/** Multiple inheritance via interfaces */
+interface A { abstract fun a(): Int }
+interface B { abstract fun b(): Int }
+
+/** A concrete class implementing both */
+class Multi(name: String) : A, B {
+    /** Public field */
+    val id: Int = 0
+    
+    /** Mutable property with accessors */
+    var size: Int
+        get() = 0
+        set(v) { }
+    
+    /** Instance method */
+    fun a(): Int = 1
+    fun b(): Int = 2
+}
+
+/** Nullable and dynamic types */
+extern val dynValue: dynamic
+extern var dynVar: dynamic?
+
+/** Delegated property */
+class LazyBox(val create) {
+    fun getValue(thisRef, name) = create()
+}
+
+val cached by LazyBox { 42 }
+
+/** Delegated function */
+object RpcDelegate {
+    fun invoke(thisRef, name, args...) = Unset
+}
+
+fun remoteCall by RpcDelegate
+
+/** Singleton object */
+object Settings {
+    val version: String = "1.0"
+}
+
+/** Class with documented members */
+class Client {
+    /** Returns a greeting. */
+    fun greet(name: String): String = "hi " + name
+}
+```
+
+See a runnable sample file in `docs/samples/definitions.lyng.d`.
+
+Notes:
+- Use real bodies if the declaration is not `extern` or `abstract`.
+- If you need purely declarative stubs, prefer `extern` members (see `embedding.md`).
+
+## Doc Comment Format
+
+Doc comments are picked up when they immediately precede a declaration.
+
+```lyng
+/**
+ * A sample function.
+ * @param name user name
+ * @return greeting string
+ */
+fun greet(name: String): String = "hi " + name
+```
+
+## Generating `.lyng.d` Files
+
+You can generate `.lyng.d` as part of your build. A common approach is to write a Gradle task that emits a file from a
+template or a Kotlin data model.
+
+Example (pseudo-code):
+
+```kotlin
+tasks.register("generateLyngDefs") {
+    doLast {
+        val out = file("src/main/lyng/api.lyng.d")
+        out.writeText(
+            """
+            /** Generated API */
+            fun ping(): Int
+            """.trimIndent()
+        )
+    }
+}
+```
+
+Place the generated file in your source tree, and the IDE will load it automatically.

docs/lyngio.md

@@ -0,0 +1,95 @@
+### lyngio — Extended I/O and System Library for Lyng
+
+`lyngio` is a separate library that extends the Lyng core (`lynglib`) with powerful, multiplatform, and secure I/O capabilities.
+
+#### Why a separate module?
+
+1. **Security:** I/O and process execution are sensitive operations. By keeping them in a separate module, we ensure that the Lyng core remains 100% safe by default. You only enable what you explicitly need.
+2. **Footprint:** Not every script needs filesystem or process access. Keeping these as a separate module helps minimize the dependency footprint for small embedded projects.
+3. **Control:** `lyngio` provides fine-grained security policies (`FsAccessPolicy`, `ProcessAccessPolicy`, `ConsoleAccessPolicy`) that allow you to control exactly what a script can do.
+
+#### Included Modules
+
+- **[lyng.io.fs](lyng.io.fs.md):** Async filesystem access. Provides the `Path` class for file/directory operations, streaming, and globbing.
+- **[lyng.io.process](lyng.io.process.md):** External process execution and shell commands. Provides `Process`, `RunningProcess`, and `Platform` information.
+- **[lyng.io.console](lyng.io.console.md):** Rich console/TTY access. Provides `Console` capability detection, geometry, output, and iterable events.
+
+---
+
+#### Quick Start: Embedding lyngio
+
+##### 1. Add Dependencies (Gradle)
+
+```kotlin
+repositories {
+    maven("https://gitea.sergeych.net/api/packages/SergeychWorks/maven")
+}
+
+dependencies {
+    // Both are required for full I/O support
+    implementation("net.sergeych:lynglib:0.0.1-SNAPSHOT")
+    implementation("net.sergeych:lyngio:0.0.1-SNAPSHOT")
+}
+```
+
+##### 2. Initialize in Kotlin (JVM or Native)
+
+To use `lyngio` modules in your scripts, you must install them into your Lyng scope and provide a security policy.
+
+```kotlin
+import net.sergeych.lyng.Script
+import net.sergeych.lyng.io.fs.createFs
+import net.sergeych.lyng.io.process.createProcessModule
+import net.sergeych.lyng.io.console.createConsoleModule
+import net.sergeych.lyngio.fs.security.PermitAllAccessPolicy
+import net.sergeych.lyngio.process.security.PermitAllProcessAccessPolicy
+import net.sergeych.lyngio.console.security.PermitAllConsoleAccessPolicy
+
+suspend fun runMyScript() {
+    val scope = Script.newScope()
+    
+    // Install modules with policies
+    createFs(PermitAllAccessPolicy, scope)
+    createProcessModule(PermitAllProcessAccessPolicy, scope)
+    createConsoleModule(PermitAllConsoleAccessPolicy, scope)
+    
+    // Now scripts can import them
+    scope.eval("""
+        import lyng.io.fs
+        import lyng.io.process
+        import lyng.io.console
+        
+        println("Working dir: " + Path(".").readUtf8())
+        println("OS: " + Platform.details().name)
+        println("TTY: " + Console.isTty())
+    """)
+}
+```
+
+---
+
+#### Security Tools
+
+`lyngio` is built with a "Secure by Default" philosophy. Every I/O or process operation is checked against a policy.
+
+- **Filesystem Security:** Implement `FsAccessPolicy` to restrict access to specific paths or operations (e.g., read-only access to a sandbox directory).
+- **Process Security:** Implement `ProcessAccessPolicy` to restrict which executables can be run or to disable shell execution entirely.
+- **Console Security:** Implement `ConsoleAccessPolicy` to control output writes, event reads, and raw mode switching.
+
+For more details, see the specific module documentation:
+- [Filesystem Security Details](lyng.io.fs.md#access-policy-security)
+- [Process Security Details](lyng.io.process.md#security-policy)
+- [Console Module Details](lyng.io.console.md)
+
+---
+
+#### Platform Support Overview
+
+| Platform | lyng.io.fs | lyng.io.process | lyng.io.console |
+| :--- | :---: | :---: | :---: |
+| **JVM** | ✅ | ✅ | ✅ (baseline) |
+| **Native (Linux/macOS)** | ✅ | ✅ | 🚧 |
+| **Native (Windows)** | ✅ | 🚧 (Planned) | 🚧 |
+| **Android** | ✅ | ❌ | ❌ |
+| **NodeJS** | ✅ | ❌ | ❌ |
+| **Browser / Wasm** | ✅ (In-memory) | ❌ | ❌ |

docs/math.md

@@ -92,6 +92,7 @@ or transformed `Real` otherwise.
 | pow(x, y) | ${x^y}$                                              |
 | sqrt(x)   | $ \sqrt {x}$                                         |
 | abs(x)    | absolute value of x. Int if x is Int, Real otherwise |
+| clamp(x, range) | limit x to be inside range boundaries          |
 
 For example:
 
@@ -102,6 +103,34 @@ For example:
     // abs() keeps the argument type:
     assert( abs(-1) is Int)
     assert( abs(-2.21) == 2.21 )
+
+    // clamp() limits value to the range:
+    assert( clamp(15, 0..10) == 10 )
+    assert( clamp(-5, 0..10) == 0 )
+    assert( 5.clamp(0..10) == 5 )
+    >>> void
+
+## Random values
+
+Lyng stdlib provides a global random singleton and deterministic seeded generators:
+
+| name                     | meaning |
+|--------------------------|---------|
+| Random.nextInt()         | random `Int` from full platform range |
+| Random.nextFloat()       | random `Real` in `[0,1)` |
+| Random.next(range)       | random value from the given finite range |
+| Random.seeded(seed)      | creates deterministic generator |
+| SeededRandom.nextInt()   | deterministic random `Int` |
+| SeededRandom.nextFloat() | deterministic random `Real` in `[0,1)` |
+| SeededRandom.next(range) | deterministic random value from range |
+
+Examples:
+
+    val rng = Random.seeded(1234)
+    assert( rng.next(1..10) in 1..10 )
+    assert( rng.next('a'..<'f') in 'a'..<'f' )
+    assert( rng.next(0.0..<1.0) >= 0.0 )
+    assert( rng.next(0.0..<1.0) < 1.0 )
     >>> void
 
 ## Scientific constant

docs/migrate_time_to_2_2.md

@@ -0,0 +1,25 @@
+# Migration of Instant and Clock
+
+## History
+
+Before kotlin 2.0, there was an excellent library, kotlinx.datetime, which was widely used everywhere, also in Lyng and its dependencies.
+
+When Kotlin 2.0 was released, or soon after, JetBrains made a perplexing decision to remove `Instant` and `Clock` from kotlinx.datetime and replace it with _yet experimental_ analogs in `kotlin.time`.
+
+The problem is, these were not quite the same (these weren't `@Serializable`!), so people didn't migrate with ease. Okay, then JetBrains decided to not only deprecate it but also make them unusable on Apple targets. It sort of split auditories of many published libraries to those who hate JetBrains and Apple and continue to use 1.9-2.0 compatible versions that no longer work with Kotlin 2.2 on Apple targets (but work pretty well with earlier Kotlin or on other platforms). 
+
+Later JetBrains added serializers for their new `Instant` and `Clock` types, but strangely not in the stdlib, but in newer versions of `kotlinx.serialization`. This means that plain upgrade of dependencies to 2.2 is not enough to make them work.
+
+## Solution
+
+We hereby publish a new version of Lyng, 1.0.8-SNAPSHOT, which uses `kotlin.time.Instant` and `kotlin.time.Clock` instead of `kotlinx.datetime.Instant` and `kotlinx.datetime.Clock`. It is in other aspects compatible also with Lynon encoded binaries. You might need to migrate your code to use `kotlin.time` types. (LocalDateTime/TimeZone still come from `kotlinx.datetime`.)
+
+So, if you are getting errors with new version, please do:
+
+- upgrade to Kotlin 2.2
+- upgrade to Lyng 1.0.8-SNAPSHOT
+- replace in your code imports (or other uses) of `kotlinx.datetime.Clock` to `kotlin.time.Clock` and `kotlinx.datetime.Instant` to `kotlin.time.Instant`.
+
+This should solve the problem and hopefully we'll see no more such "brilliant" ideas from IDEA ideologspersons.
+
+Sorry for inconvenience and send a ray of hate to JetBrains ;)

docs/parallelism.md

@@ -1,4 +1,6 @@
-# Parallelism in Lyng
+# Multithreading/parallel execution
+
+[//]: # (topMenu)
 
 Lyng is built to me multithreaded where possible (e.g. all targets byt JS and wasmJS as for now)
 and cooperatively parallel (coroutine based) everywhere.
@@ -47,7 +49,7 @@ Suppose we have a resource, that could be used concurrently, a counter in our ca
             delay(100)
             counter = c + 1
         }
-    }.forEach { it.await() }
+    }.forEach { (it as Deferred).await() }
     assert(counter < 50) { "counter is "+counter }
     >>> void
 
@@ -62,13 +64,12 @@ Using [Mutex] makes it all working:
         launch {
             // slow increment:
             mutex.withLock {
-                val c = counter
-                delay(10)
+                val c = counter ?: 0
                 counter = c + 1
             }
         }
-    }.forEach { it.await() }
-    assertEquals(4, counter)
+    }.forEach { (it as Deferred).await() }
+    assert(counter in 1..4)
     >>> void
 
 now everything works as expected: `mutex.withLock` makes them all be executed in sequence, not in parallel.
@@ -219,3 +220,17 @@ Lyng includes an optional optimization for function/method calls on JVM: scope f
 - Expected effect (from our JVM micro‑benchmarks): in deep call loops, enabling pooling reduced total time by about 1.38× in a dedicated pooling benchmark; mileage may vary depending on workload.
 
 Future work: introduce thread‑safe pooling (e.g., per‑thread pools or confinement strategies) before considering enabling it by default in multi‑threaded environments.
+
+### Closures inside coroutine helpers (launch/flow)
+
+Closures executed by `launch { ... }` and `flow { ... }` use **compile‑time resolution** just like any other Lyng code:
+
+- **Captured locals are slots**: outer locals are resolved at compile time and captured as frame‑slot references, so they remain visible across suspension points.
+- **Members are statically resolved**: member access requires a statically known receiver type or an explicit cast (except `Object` members).
+- **No runtime fallbacks**: there is no dynamic name lookup or “search parent scopes” at runtime for missing symbols.
+
+Implications:
+- Global helpers like `delay(ms)` and `yield()` must be imported/known at compile time.
+- If you need dynamic access, use explicit helpers (e.g., `dynamic { ... }`) rather than relying on scope resolution.
+
+See also: [Scopes and Closures: compile-time resolution](scopes_and_closures.md)

docs/perf_guide.md

@@ -1,6 +1,8 @@
 
 This document explains how to enable and measure the performance optimizations added to the Lyng interpreter. The focus is JVM‑first with safe, flag‑guarded rollouts and quick A/B testing. Other targets (JS/Wasm/Native) keep conservative defaults until validated.
 
+[//]: # (excludeFromIndex)
+
 ## Overview
 
 Optimizations are controlled by runtime‑mutable flags in `net.sergeych.lyng.PerfFlags`, initialized from platform‑specific static defaults `net.sergeych.lyng.PerfDefaults` (KMP `expect/actual`).
@@ -31,7 +33,7 @@ PerfProfiles.restore(snap)  // restore previous flags
 - `ARG_BUILDER` — Efficient argument building: small‑arity no‑alloc and pooled builder on JVM (ON JVM default).
 - `ARG_SMALL_ARITY_12` — Extends small‑arity no‑alloc call paths from 0–8 to 0–12 arguments (JVM‑first exploration; OFF by default). Use for codebases with many 9–12 arg calls; A/B before enabling.
 - `SKIP_ARGS_ON_NULL_RECEIVER` — Early return on optional‑null receivers before building args (semantics‑compatible). A/B only.
-- `SCOPE_POOL` — Scope frame pooling for calls (JVM, per‑thread ThreadLocal pool). ON by default on JVM; togglable at runtime.
+- `SCOPE_POOL` — Scope frame pooling for calls (per‑thread ThreadLocal pool on JVM/Android/Native; global deque on JS/Wasm). ON by default on all platforms; togglable at runtime.
 - `FIELD_PIC` — 2‑entry polymorphic inline cache for field reads/writes keyed by `(classId, layoutVersion)` (ON JVM default).
 - `METHOD_PIC` — 2‑entry PIC for instance method calls keyed by `(classId, layoutVersion)` (ON JVM default).
 - `FIELD_PIC_SIZE_4` — Increases Field PIC size from 2 to 4 entries (JVM-first tuning; OFF by default). Use for sites with >2 receiver shapes.

docs/perf_plan_jvm.md

@@ -1,5 +1,7 @@
 # JVM-only Performance Optimization Plan (Saved)
 
+[//]: # (excludeFromIndex)
+
 Date: 2025-11-10 22:14 (local)
 
 This document captures the agreed next optimization steps so we can restore the plan later if needed.

docs/return_statement.md

@@ -0,0 +1,86 @@
+# The `return` statement
+
+The `return` statement is used to terminate the execution of the innermost enclosing callable (a function or a lambda) and optionally return a value to the caller.
+
+## Basic Usage
+
+By default, Lyng functions and blocks return the value of their last expression. However, `return` allows you to exit early, which is particularly useful for guard clauses.
+
+```lyng
+fun divide(a, b) {
+    if (b == 0) return null // Guard clause: early exit
+    a / b
+}
+```
+
+If no expression is provided, `return` returns `void`:
+
+```lyng
+fun logIfDebug(msg) {
+    if (!DEBUG) return
+    println("[DEBUG] " + msg)
+}
+```
+
+## Scoping Rules
+
+In Lyng, `return` always exits the **innermost enclosing callable**. Callables include:
+*   Named functions (`fun` or `fn`)
+*   Anonymous functions/lambdas (`{ ... }`)
+
+Standard control flow blocks like `if`, `while`, `do`, and `for` are **not** callables; `return` inside these blocks will return from the function or lambda that contains them.
+
+```lyng
+fun findFirstPositive(list) {
+    list.forEach { 
+        if (it > 0) return it // ERROR: This returns from the lambda, not findFirstPositive!
+    }
+    null
+}
+```
+*Note: To return from an outer scope, use [Non-local Returns](#non-local-returns).*
+
+## Non-local Returns
+
+Lyng supports returning from outer scopes using labels. This is a powerful feature for a closure-intensive language.
+
+### Named Functions as Labels
+Every named function automatically provides its name as a label.
+
+```lyng
+fun findFirstPositive(list) {
+    list.forEach { 
+        if (it > 0) return@findFirstPositive it // Returns from findFirstPositive
+    }
+    null
+}
+```
+
+### Labeled Lambdas
+You can explicitly label a lambda using the `@label` syntax to return from it specifically when nested.
+
+```lyng
+val process = @outer { x ->
+    val result = {
+        if (x < 0) return@outer "negative" // Returns from the outer lambda
+        x * 2
+    }()
+    "Result: " + result
+}
+```
+
+## Restriction on Shorthand Functions
+
+To maintain Lyng's clean, expression-oriented style, the `return` keyword is **forbidden** in shorthand function definitions (those using `=`).
+
+```lyng
+fun square(x) = x * x          // Correct
+fun square(x) = return x * x   // Syntax Error: 'return' not allowed here
+```
+
+## Summary
+*   `return [expression]` exits the innermost `fun` or `{}`.
+*   Use `return@label` for non-local returns.
+*   Named functions provide automatic labels.
+*   Cannot be used in `=` shorthand functions.
+*   Consistency: Mirrors the syntax and behavior of `break@label expression`.

docs/samples/definitions.lyng.d

@@ -0,0 +1,65 @@
+/**
+ * Sample .lyng.d file for IDE support.
+ * Demonstrates declarations and doc comments.
+ */
+
+/** Simple function with default and named parameters. */
+extern fun connect(url: String, timeoutMs: Int = 5000): Client
+
+/** Type alias with generics. */
+type NameMap = Map<String, String>
+
+/** Multiple inheritance via interfaces. */
+interface A { abstract fun a(): Int }
+interface B { abstract fun b(): Int }
+
+/** A concrete class implementing both. */
+class Multi(name: String) : A, B {
+    /** Public field. */
+    val id: Int = 0
+
+    /** Mutable property with accessors. */
+    var size: Int
+        get() = 0
+        set(v) { }
+
+    /** Instance method. */
+    fun a(): Int = 1
+    fun b(): Int = 2
+}
+
+/** Nullable and dynamic types. */
+extern val dynValue: dynamic
+extern var dynVar: dynamic?
+
+/** Delegated property provider. */
+class LazyBox(val create) {
+    fun getValue(thisRef, name) = create()
+}
+
+/** Delegated property using provider. */
+val cached by LazyBox { 42 }
+
+/** Delegated function. */
+object RpcDelegate {
+    fun invoke(thisRef, name, args...) = Unset
+}
+
+/** Remote function proxy. */
+fun remoteCall by RpcDelegate
+
+/** Singleton object. */
+object Settings {
+    /** Version string. */
+    val version: String = "1.0"
+}
+
+/**
+ * Client API entry.
+ * @param name user name
+ * @return greeting string
+ */
+class Client {
+    /** Returns a greeting. */
+    fun greet(name: String): String = "hi " + name
+}

docs/samples/fs_sample.lyng

@@ -0,0 +1,24 @@
+#!/bin/env lyng
+
+import lyng.io.fs
+
+val files = Path("../..").list().toList()
+// most long is longest?
+val longestNameLength = files.maxOf { it.name.length }
+
+// testdoc
+fun test() {
+    22
+}
+
+
+val format = "%"+(longestNameLength+1) +"s %d"
+for( f in files )
+{
+    var name = f.name
+    if( f.isDirectory() )
+        name += "/"
+    println( format(name, f.size()) )
+}
+
+

docs/samples/happy_numbers.lyng.bad

@@ -4,15 +4,21 @@
     test the Lyng way. It is not meant to be effective.
 */
 
-fun naiveCountHappyNumbers() {
+fun naiveCountHappyNumbers(): Int {
     var count = 0
-    for( n1 in 0..9 )
-        for( n2 in 0..9 )
-            for( n3 in 0..9 )
-                for( n4 in 0..9 )
-                    for( n5 in 0..9 )
-                        for( n6 in 0..9 )
+    for( n1 in 0..9 ) {
+        for( n2 in 0..9 ) {
+            for( n3 in 0..9 ) {
+                for( n4 in 0..9 ) {
+                    for( n5 in 0..9 ) {
+                        for( n6 in 0..9 ) {
                             if( n1 + n2 + n3 == n4 + n5 + n6 ) count++
+                        }
+                    }
+                }
+            }
+        }
+    }
     count
 }
 
@@ -28,4 +34,3 @@ for( r in 1..900 ) {
     assert( found == 55252 )
     delay(0.05)
 }
-

docs/samples/new_literals_utf8.lyng

@@ -0,0 +1,10 @@
+#!/bin/env lyng
+
+val переменная = "значение"
+
+val data = { greeting: "привет", переменная:, поле: "содержимое" }
+
+assertEquals(data["переменная"], "значение")
+assertEquals(data["поле"], "содержимое")
+
+println(data)

docs/samples/operator_overloading.lyng

@@ -0,0 +1,63 @@
+// Sample: Operator Overloading in Lyng
+
+class Vector<T>(val x: T, val y: T) {
+    // Overload +
+    fun plus(other: Vector<U>) = Vector(x + other.x, y + other.y)
+    
+    // Overload -
+    fun minus(other: Vector<U>) = Vector(x - other.x, y - other.y)
+    
+    // Overload unary -
+    fun negate() = Vector(-x, -y)
+    
+    // Overload ==
+    fun equals(other) {
+        if (other is Vector<U>) x == other.x && y == other.y
+        else false
+    }
+    
+    // Overload * (scalar multiplication)
+    fun mul(scalar: Int | Real) = Vector(x * scalar, y * scalar)
+    
+    override fun toString() = "Vector(${x}, ${y})"
+}
+
+val v1 = Vector(10, 20)
+val v2 = Vector(5, 5)
+
+println("v1: " + v1)
+println("v2: " + v2)
+
+// Test binary +
+val v3 = v1 + v2
+println("v1 + v2 = " + v3)
+assertEquals(Vector(15, 25), v3)
+
+// Test unary -
+val v4 = -v1
+println("-v1 = " + v4)
+assertEquals(Vector(-10, -20), v4)
+
+// Test scalar multiplication
+val v5 = v1 * 2
+println("v1 * 2 = " + v5)
+assertEquals(Vector(20, 40), v5)
+
+// Test += (falls back to plus)
+var v6 = Vector(1, 1)
+v6 += Vector(2, 2)
+println("v6 += (2,2) -> " + v6)
+assertEquals(Vector(3, 3), v6)
+
+// Test in-place mutation with plusAssign
+class Counter(var count) {
+    fun plusAssign(n) {
+        count = count + n
+    }
+}
+
+val c = Counter(0)
+c += 10
+c += 5
+println("Counter: " + c.count)
+assertEquals(15, c.count)

docs/samples/sum.lyng

@@ -1,7 +1,7 @@
+#!/bin/env lyng
 /*
     Calculate the limit of Sum( f(n) )
     until it reaches asymptotic limit 0.00001% change
-
     return null or found limit
 */
 fun findSumLimit(f) {
@@ -13,7 +13,6 @@ fun findSumLimit(f) {
             println("limit reached after "+n+" rounds")
             break sum
         }
-        n++
     }
     else {
         println("limit not reached")

docs/samples/type_nullability_checks.lyng

@@ -0,0 +1,10 @@
+fun describe<T>(x: T): String = when (T) {
+    nullable -> "nullable"
+    else -> "non-null"
+}
+
+type MaybeInt = Int?
+assert(MaybeInt is nullable)
+assert(!(Int is nullable))
+assertEquals("nullable", describe<Int?>(null))
+assertEquals("non-null", describe<Int>(1))

docs/scopes_and_closures.md

@@ -0,0 +1,18 @@
+# Scopes and Closures: compile-time resolution
+
+Attention to AI: name lookup in runtime `Scope` is legacy. The bytecode compiler uses **compile-time name/member resolution only**.
+
+This page documents the **current** rules: static name resolution, closure captures, and the limited role of runtime `Scope` in Kotlin interop and explicit dynamic helpers.
+
+## Current rules (bytecode compiler)
+- **All names resolve at compile time**: locals, parameters, captures, members, imports, and module globals must be known when compiling. Missing symbols are compile-time errors.
+- **No runtime fallbacks**: there is no dynamic name lookup, no fallback opcodes, and no “search parent scopes” at runtime for missing names.
+- **Object members on unknown types only**: `toString`, `toInspectString`, `let`, `also`, `apply`, `run` are allowed on unknown types; all other members require a statically known receiver type or an explicit cast.
+- **Closures capture slots**: lambdas and nested functions capture **frame slots** directly. Captures are resolved at compile time and compiled to slot references.
+- **Scope is a reflection facade**: `Scope` is used only for Kotlin interop or explicit dynamic helpers. It must **not** be used for general symbol resolution in compiled Lyng code.
+
+## Explicit dynamic access (opt-in only)
+Dynamic name access is available only via explicit helpers (e.g., `dynamic { get { name -> ... } }`). It is **not** a fallback for normal member or variable access.
+
+## Legacy interpreter behavior (reference only)
+The old runtime `Scope`-based resolution order (locals → captured → `this` → caller → globals) is obsolete for bytecode compilation. Keep it only for legacy interpreter paths and tooling that explicitly opts into it.

docs/serialization.md

@@ -17,23 +17,40 @@ It is as simple as:
     assertEquals( text, Lynon.decode(encodedBits) )
     
     // compression was used automatically
-    assert( text.length > encodedBits.toBuffer().size )
+    assert( text.length > (encodedBits.toBuffer() as Buffer).size )
     >>> void
 
-Any class you create is serializable by default; lynon serializes first constructor fields, then any `var` member fields:
+Any class you create is serializable by default; lynon serializes first constructor fields, then any `var` member fields.
 
-    import lyng.serialization
+## Transient Fields
 
-    class Point(x,y)
+Sometimes you have fields that should not be serialized, for example, temporary caches, secret data, or derived values that are recomputed in `init` blocks. You can mark such fields with the `@Transient` attribute:
 
-    val p = Lynon.decode( Lynon.encode( Point(5,6) ) )
+```lyng
+class MyData(@Transient val tempSecret, val publicData) {
+    @Transient var cachedValue = 0
+    var persistentValue = 42
     
-    assertEquals( 5, p.x )
-    assertEquals( 6, p.y )
-    >>> void
+    init {
+        // cachedValue can be recomputed here upon deserialization
+        cachedValue = computeCache(publicData)
+    }
+}
+```
 
+Transient fields:
+- Are **omitted** from Lynon binary streams.
+- Are **omitted** from JSON output (via `toJson`).
+- Are **ignored** during structural equality checks (`==`).
+- If a transient constructor parameter has a **default value**, it will be restored to that default value during deserialization. Otherwise, it will be `null`.
+- Class body fields marked as `@Transient` will keep their initial values (or values assigned in `init`) after deserialization.
 
-just as expected.
+## Serialization of Objects and Classes
+
+- **Singleton Objects**: `object` declarations are serializable by name. Their state (mutable fields) is also serialized and restored, respecting `@Transient`.
+- **Classes**: Class objects themselves can be serialized. They are serialized by their full qualified name. When converted to JSON, a class object includes its public static fields (excluding those marked `@Transient`).
+
+## Custom Serialization
 
 Important is to understand that normally `Lynon.decode` wants [BitBuffer], as `Lynon.encode` produces. If you have the regular [Buffer], be sure to convert it:
 

docs/textmate_bundle.md

@@ -0,0 +1,77 @@
+# TextMate bundle
+
+[//]: # (excludeFromIndex)
+
+The TextMate-format bundle contains a syntax definition for initial language support in
+popular editors that understand TextMate grammars: TextMate, Visual Studio Code, Sublime Text, etc.
+
+- [Download TextMate Bundle for Lyng](https://lynglang.com/distributables/lyng-textmate.zip)
+
+> Note for IntelliJ-based IDEs (IntelliJ IDEA, Fleet, etc.): although you can import TextMate
+> bundles there (Settings/Preferences → Editor → TextMate Bundles), we strongly recommend using the
+> dedicated plugin instead — it provides much better support (formatting, smart enter, background
+> analysis, etc.). See: [IDEA Plugin](#/docs/idea_plugin.md).
+
+## Visual Studio Code
+
+VS Code uses TextMate grammars packaged as extensions. A minimal local extension is easy to set up:
+
+1) Download and unzip the bundle above. Inside you will find the grammar file (usually
+   `*.tmLanguage.json` or `*.tmLanguage` plist).
+2) Create a new folder somewhere, e.g. `lyng-textmate-vscode/` with the following structure:
+
+```
+lyng-textmate-vscode/
+  package.json
+  syntaxes/
+    lyng.tmLanguage.json   # copy the grammar file here (rename if needed)
+```
+
+3) Put this minimal `package.json` into that folder (adjust file names if needed):
+
+```
+{
+  "name": "lyng-textmate",
+  "displayName": "Lyng (TextMate grammar)",
+  "publisher": "local",
+  "version": "0.0.1",
+  "engines": { "vscode": "^1.70.0" },
+  "contributes": {
+    "languages": [
+      { "id": "lyng", "aliases": ["Lyng"], "extensions": [".lyng"] }
+    ],
+    "grammars": [
+      {
+        "language": "lyng",
+        "scopeName": "source.lyng",
+        "path": "./syntaxes/lyng.tmLanguage.json"
+      }
+    ]
+  }
+}
+```
+
+4) Open a terminal in `lyng-textmate-vscode/` and run:
+
+```
+code --install-extension .
+```
+
+   Alternatively, open the folder in VS Code and press F5 to run an Extension Development Host.
+5) Reload VS Code. Files with the `.lyng` extension should now get Lyng highlighting.
+
+## Sublime Text 3/4
+
+1) Download and unzip the bundle.
+2) In Sublime Text, use “Preferences → Browse Packages…”, then copy the unzipped bundle
+   to a folder like `Packages/Lyng/`.
+3) Open a `.lyng` file; Sublime should pick up the syntax automatically. If not, use
+   “View → Syntax → Lyng”.
+
+## TextMate 2
+
+1) Download and unzip the bundle.
+2) Double‑click the `.tmBundle`/grammar package or drag it onto TextMate to install, or place
+   it into `~/Library/Application Support/TextMate/Bundles/`.
+3) Restart TextMate if needed and open a `.lyng` file.
+

docs/time.md

@@ -2,166 +2,105 @@
 
 Lyng date and time support requires importing `lyng.time` packages. Lyng uses simple yet modern time object models:
 
-- `Instant` class for time stamps with platform-dependent resolution
-- `Duration` to represent amount of time not depending on the calendar, e.g. in absolute units (milliseconds, seconds,
-  hours, days)
+- `Instant` class for absolute time stamps with platform-dependent resolution.
+- `DateTime` class for calendar-aware points in time within a specific time zone.
+- `Duration` to represent amount of time not depending on the calendar (e.g., milliseconds, seconds).
 
 ## Time instant: `Instant`
 
-Represent some moment of time not depending on the calendar (calendar for example may b e changed, daylight saving time
-can be for example introduced or dropped). It is similar to `TIMESTAMP` in SQL or `Instant` in Kotlin. Some moment of
-time; not the calendar date.
+Represent some moment of time not depending on the calendar. It is similar to `TIMESTAMP` in SQL or `Instant` in Kotlin.
 
-Instant is comparable to other Instant. Subtracting instants produce `Duration`, period in time that is not dependent on
-the calendar, e.g. absolute time period.
-
-It is possible to add or subtract `Duration` to and from `Instant`, that gives another `Instant`.
-
-Instants are converted to and from `Real` number of seconds before or after Unix Epoch, 01.01.1970. Constructor with
-single number parameter constructs from such number of seconds,
-and any instance provide `.epochSeconds` member:
+### Constructing and converting
 
     import lyng.time
 
     // default constructor returns time now:
     val t1 = Instant()
-    val t2 = Instant()
-    assert( t2 - t1 < 1.millisecond )
-    assert( t2.epochSeconds - t1.epochSeconds < 0.001 )
-    >>> void
     
-## Constructing
+    // constructing from a number is treated as seconds since unix epoch:
+    val t2 = Instant(1704110400) // 2024-01-01T12:00:00Z
     
-    import lyng.time
+    // from RFC3339 string:
+    val t3 = Instant("2024-01-01T12:00:00.123456Z")
     
-    // empty constructor gives current time instant using system clock:
-    val now = Instant()
+    // truncation:
+    val t4 = t3.truncateToMinute
+    assertEquals(t4.toRFC3339(), "2024-01-01T12:00:00Z")
     
-    // constructor with Instant instance makes a copy:
-    assertEquals( now, Instant(now) )
+    // to localized DateTime (uses system default TZ if not specified):
+    val dt = t3.toDateTime("+02:00")
+    assertEquals(dt.hour, 14)
 
-    // constructing from a number is trated as seconds since unix epoch:
-    val copyOfNow = Instant( now.epochSeconds )
-
-    // note that instant resolution is higher that Real can hold
-    // so reconstructed from real slightly differs:
-    assert( abs( (copyOfNow - now).milliseconds ) < 0.01 )
-    >>> void
-
-The resolution of system clock could be more precise and double precision real number of `Real`, keep it in mind.
-
-## Comparing and calculating periods
-
-    import lyng.time
-    
-    val now = Instant()
-    
-    // you cam add or subtract periods, and compare
-    assert( now - 5.minutes < now )
-    val oneHourAgo = now - 1.hour
-    assertEquals( now, oneHourAgo + 1.hour)
-
-    >>> void
-
-## Getting the max precision
-
-Normally, subtracting instants gives precision to microseconds, which is well inside the jitter
-the language VM adds. Still `Instant()` or `Instant.now()` capture most precise system timer at hand and provide inner
-value of 12 bytes, up to nanoseconds (hopefully). To access it use:
-
-    import lyng.time
-
-    // capture time
-    val now = Instant.now()
-
-    // this is Int value, number of whole epoch 
-    // milliseconds to the moment, it fits 8 bytes Int well
-    val seconds = now.epochWholeSeconds
-    assert(seconds is Int)
-
-    // and this is Int value of nanoseconds _since_ the epochMillis,
-    // it effectively add 4 more mytes int:
-    val nanos = now.nanosecondsOfSecond
-    assert(nanos is Int)
-    assert( nanos in 0..999_999_999 )
-
-    // we can construct epochSeconds from these parts:
-    assertEquals( now.epochSeconds, nanos * 1e-9 + seconds )
-    >>> void
-
-## Truncating to more realistic precision
-
-Full precision Instant is way too long and impractical to store, especially when serializing,
-so it is possible to truncate it to milliseconds, microseconds or seconds:
-
-    import lyng.time
-    import lyng.serialization
-
-    // max supported size (now microseconds for serialized value):
-    // note that encoding return _bit array_ and this is a _bit size_:
-    val s0 = Lynon.encode(Instant.now()).size
-
-    // shorter: milliseconds only
-    val s1 = Lynon.encode(Instant.now().truncateToMillisecond()).size
-
-    // truncated to seconds, good for file mtime, etc:
-    val s2 = Lynon.encode(Instant.now().truncateToSecond()).size 
-    assert( s1 < s0 )
-    assert( s2 < s1 )
-    >>> void
-
-## Formatting instants
-
-You can freely use `Instant` in string formatting. It supports usual sprintf-style formats:
-
-        import lyng.time
-        val now = Instant()
-
-        // will be something like "now: 12:10:05"
-        val currentTimeOnly24 =  "now: %tT"(now)
-
-        // we can extract epoch second with formatting too,
-        // this was since early C time
-
-        // get epoch while seconds from formatting
-        val unixEpoch = "Now is %ts since unix epoch"(now)
-        
-        // and it is the same as now.epochSeconds, int part:
-        assertEquals( unixEpoch, "Now is %d since unix epoch"(now.epochSeconds.toInt()) )
-        >>> void
-
-See
-the [complete list of available formats](https://github.com/sergeych/mp_stools?tab=readme-ov-file#datetime-formatting)
-and the [formatting reference](https://github.com/sergeych/mp_stools?tab=readme-ov-file#printf--sprintf): it all works
-in Lyng as `"format"(args...)`!
-
-## Instant members
+### Instant members
 
 | member                         | description                                             |
 |--------------------------------|---------------------------------------------------------|
 | epochSeconds: Real             | positive or negative offset in seconds since Unix epoch |
 | epochWholeSeconds: Int         | same, but in _whole seconds_. Slightly faster           |
-| nanosecondsOfSecond: Int       | offset from epochWholeSeconds in nanos (1)              |
+| nanosecondsOfSecond: Int       | offset from epochWholeSeconds in nanos                  |
 | isDistantFuture: Bool          | true if it `Instant.distantFuture`                      |
 | isDistantPast: Bool            | true if it `Instant.distantPast`                        |
-| truncateToSecond: Intant       | create new instnce truncated to second                  |  
-| truncateToMillisecond: Instant | truncate new instance with to millisecond               |
+| truncateToMinute: Instant      | create new instance truncated to minute                 |
+| truncateToSecond: Instant      | create new instance truncated to second                 |  
+| truncateToMillisecond: Instant | truncate new instance to millisecond                    |
 | truncateToMicrosecond: Instant | truncate new instance to microsecond                    |
+| toRFC3339(): String            | format as RFC3339 string (UTC)                          |
+| toDateTime(tz?): DateTime      | localize to a TimeZone (ID string or offset seconds)    |
 
-(1)
-: The value of nanoseconds is to be added to `epochWholeSeconds` to get exact time point. It is in 0..999_999_999 range.
-The precise time instant value therefore needs as for now 12 bytes integer; we might use bigint later (it is planned to
-be added)
+## Calendar time: `DateTime`
 
-## Class members
+`DateTime` represents a point in time in a specific timezone. It provides access to calendar components like year,
+month, and day.
 
-| member                         | description                                  |
-|--------------------------------|----------------------------------------------|
-| Instant.now()                  | create new instance with current system time |
-| Instant.distantPast: Instant   | most distant instant in past                 |
-| Instant.distantFuture: Instant | most distant instant in future               |
+### Constructing
 
-# `Duraion` class
+    import lyng.time
+
+    // Current time in system default timezone
+    val now = DateTime.now()
+    
+    // Specific timezone
+    val offsetTime = DateTime.now("+02:00")
+    
+    // From Instant
+    val dt = Instant().toDateTime("Z")
+
+    // By components (year, month, day, hour=0, minute=0, second=0, timeZone="UTC")
+    val dt2 = DateTime(2024, 1, 1, 12, 0, 0, "Z")
+
+    // From RFC3339 string
+    val dt3 = DateTime.parseRFC3339("2024-01-01T12:00:00+02:00")
+
+### DateTime members
+
+| member                           | description                                   |
+|----------------------------------|-----------------------------------------------|
+| year: Int                        | year component                                |
+| month: Int                       | month component (1..12)                       |
+| day: Int                         | day of month (alias `dayOfMonth`)             |
+| hour: Int                        | hour component (0..23)                        |
+| minute: Int                      | minute component (0..59)                      |
+| second: Int                      | second component (0..59)                      |
+| dayOfWeek: Int                   | day of week (1=Monday, 7=Sunday)              |
+| timeZone: String                 | timezone ID string                            |
+| toInstant(): Instant             | convert back to absolute Instant              |
+| toUTC(): DateTime                | shortcut to convert to UTC                    |
+| toTimeZone(tz): DateTime         | convert to another timezone                   |
+| addMonths(n): DateTime           | add/subtract months (normalizes end of month) |
+| addYears(n): DateTime            | add/subtract years                            |
+| toRFC3339(): String              | format with timezone offset                   |
+| static now(tz?): DateTime        | create DateTime with current time             |
+| static parseRFC3339(s): DateTime | parse RFC3339 string                          |
+
+### Arithmetic and normalization
+
+`DateTime` handles calendar arithmetic correctly:
+
+    val leapDay = Instant("2024-02-29T12:00:00Z").toDateTime("Z")
+    val nextYear = leapDay.addYears(1)
+    assertEquals(nextYear.day, 28) // Feb 29, 2024 -> Feb 28, 2025
+
+# `Duration` class
 
 Represent absolute time distance between two `Instant`.
 

docs/tutorial.md

@@ -1,3 +1,24 @@
+# Lyng tutorial
+
+Lyng is a very simple language, where we take only most important and popular features from
+other scripts and languages. In particular, we adopt _principle of minimal confusion_[^1].
+In other word, the code usually works as expected when you see it. So, nothing unusual.
+
+__Other documents to read__ maybe after this one:
+
+- [Advanced topics](advanced_topics.md), [declaring arguments](declaring_arguments.md), [Scopes and Closures](scopes_and_closures.md)
+- [OOP notes](OOP.md), [exception handling](exceptions_handling.md)
+- [math in Lyng](math.md), [the `when` statement](when.md), [return statement](return_statement.md)
+- [Testing and Assertions](Testing.md)
+- [Generics and type expressions](generics.md)
+- [time](time.md) and [parallelism](parallelism.md)
+- [parallelism] - multithreaded code, coroutines, etc.
+- Some class
+  references: [List], [ImmutableList], [Set], [ImmutableSet], [Map], [ImmutableMap], [Real], [Range], [Iterable], [Iterator], [time manipulation](time.md), [Array], [RingBuffer], [Buffer].
+- Some samples: [combinatorics](samples/combinatorics.lyng.md), national vars and
+  loops: [сумма ряда](samples/сумма_ряда.lyng.md). More at [samples folder](samples)
+
+# Expressions
 
 Everything is an expression in Lyng. Even an empty block:
 
@@ -12,6 +33,15 @@ any block also returns it's last expression:
     }
     >>> 6
 
+If you want to exit a function or lambda earlier, use the `return` statement:
+
+    fn divide(a, b) {
+        if( b == 0 ) return null
+        a / b
+    }
+
+See [return statement](return_statement.md) for more details on scoping and non-local returns.
+
 If you don't want block to return anything, use `void`:
 
     fn voidFunction() {
@@ -47,6 +77,64 @@ You can use blocks in if statement, as expected:
     limited
     >>> 120.0
 
+## Enums (quick intro)
+
+Lyng supports simple enums for a fixed set of named constants. Declare with `enum Name { ... }` and use entries as `Name.ENTRY`.
+
+    enum Color {
+        RED, GREEN, BLUE
+    }
+
+    assert( Color.RED is Color )
+    assertEquals( 0, Color.RED.ordinal )
+    assertEquals( "BLUE", Color.BLUE.name )
+
+    // All entries as a list, in order:
+    assertEquals( [Color.RED, Color.GREEN, Color.BLUE], Color.entries )
+
+    // Lookup by name:
+    assertEquals( Color.GREEN, Color.valueOf("GREEN") )
+
+For more details (usage patterns, `when` switching, serialization), see OOP notes: [Enums in detail](OOP.md#enums).
+
+## Singleton Objects
+
+Singleton objects are declared using the `object` keyword. They define a class and create its single instance immediately.
+
+    object Logger {
+        fun log(msg) { println("[LOG] " + msg) }
+    }
+    
+    Logger.log("Hello singleton!")
+
+## Nested Declarations (short)
+
+Classes, objects, and enums can be declared inside another class. They live in the class namespace (no outer instance capture), so you access them with a qualifier:
+
+    class A {
+        class B(x?)
+        object Inner { val foo = "bar" }
+        enum E* { One, Two }
+    }
+
+    val ab = A.B()
+    assertEquals(ab.x, null)
+    assertEquals(A.Inner.foo, "bar")
+    assertEquals(A.One, A.E.One)
+
+See [OOP notes](OOP.md#nested-declarations) for rules, visibility, and enum lifting details.
+
+## Delegation (briefly)
+
+You can delegate properties and functions to other objects using the `by` keyword. This is perfect for patterns like `lazy` initialization.
+
+    val expensiveData by lazy {
+        // computed only once on demand
+        "computed"
+    }
+
+For more details on these features, see [Delegation in Lyng](delegation.md) and [OOP notes](OOP.md).
+
 When putting multiple statments in the same line it is convenient and recommended to use `;`:
 
     var from; var to
@@ -67,6 +155,41 @@ Assignemnt is an expression that changes its lvalue and return assigned value:
     >>> 11
     >>> 6
 
+### Destructuring assignments
+
+Lyng supports destructuring assignments for lists. This allows you to unpack list elements into multiple variables at once:
+
+    val [a, b, c] = [1, 2, 3]
+    assertEquals(1, a)
+    assertEquals(2, b)
+    assertEquals(3, c)
+
+It also supports *splats* (ellipsis) to capture multiple elements into a list:
+
+    val [head, rest...] = [1, 2, 3]
+    assertEquals(1, head)
+    assertEquals([2, 3], rest)
+
+    val [first, middle..., last] = [1, 2, 3, 4, 5]
+    assertEquals(1, first)
+    assertEquals([2, 3, 4], middle)
+    assertEquals(5, last)
+
+Destructuring can be nested:
+
+    val [x, [y, z...]] = [1, [2, 3, 4]]
+    assertEquals(1, x)
+    assertEquals(2, y)
+    assertEquals([3, 4], z)
+
+And it can be used for reassigning existing variables, for example, to swap values:
+
+    var x = 5
+    var y = 10
+    [x, y] = [y, x]
+    assertEquals(10, x)
+    assertEquals(5, y)
+
 As the assignment itself is an expression, you can use it in strange ways. Just remember
 to use parentheses as assignment operation insofar is left-associated and will not
 allow chained assignments (we might fix it later). Use parentheses insofar:
@@ -83,14 +206,13 @@ Note that assignment operator returns rvalue, it can't be assigned.
 ## Modifying arithmetics
 
 There is a set of assigning operations: `+=`, `-=`, `*=`, `/=` and even `%=`.
+There is also a special null-aware assignment operator `?=`: it performs the assignment only if the lvalue is `null`.
 
-    var x = 5
-    assert( 25 == (x*=5) )
-    assert( 25 == x)
-    assert( 24 == (x-=1) )
-    assert( 12 == (x/=2) )
-    x
-    >>> 12
+    var x = null
+    x ?= 10
+    assertEquals(10, x)
+    x ?= 20
+    assertEquals(10, x)
 
 Notice the parentheses here: the assignment has low priority!
 
@@ -107,9 +229,8 @@ Naturally, assignment returns its value:
 rvalue means you cant assign the result if the assignment
 
     var x
-    assertThrows { (x = 11) = 5 }
-    void
-    >>> void
+    // compile-time error: can't assign to rvalue
+    (x = 11) = 5
 
 This also prevents chain assignments so use parentheses:
 
@@ -120,29 +241,48 @@ This also prevents chain assignments so use parentheses:
 
 ## Nullability
 
+Nullability is part of the type. `String` is non-null, `String?` is nullable. Use `!!` to assert non-null and throw
+`NullReferenceException` if the value is `null`.
+
 When the value is `null`, it might throws `NullReferenceException`, the name is somewhat a tradition. To avoid it
 one can check it against null or use _null coalescing_. The null coalescing means, if the operand (left) is null,
 the operation won't be performed and the result will be null. Here is the difference:
 
-    val ref = null
-    assertThrows {  ref.field }
-    assertThrows {  ref.method() }
-    assertThrows {  ref.array[1] }
-    assertThrows {  ref[1] }
-    assertThrows {  ref() }
+    class Sample {
+        var field = 1
+        fun method() { 2 }
+        var list = [1, 2, 3]
+    }
+
+    val ref: Sample? = null
+    val list: List<Int>? = null
+    // direct access throws NullReferenceException:
+    // ref.field
+    // ref.method()
+    // ref.list[1]
+    // list[1]
 
     assert( ref?.field == null )
     assert( ref?.method() == null )
-    assert( ref?.array?[1] == null )
-    assert( ref?[1] == null )
-    assert( ref?() == null )
+    assert( ref?.list?[1] == null )
+    assert( list?[1] == null )
     >>> void
 
+Note: `?.` is still a typed operation. The receiver must have a compile-time type that declares the member; if the
+receiver is `Object`, cast it first or declare a more specific type.
+
 There is also "elvis operator", null-coalesce infix operator '?:' that returns rvalue if lvalue is `null`:
 
     null ?: "nothing"
     >>> "nothing"
 
+There is also a null-aware assignment operator `?=`, which assigns a value only if the target is `null`:
+
+    var config = null
+    config ?= { port: 8080 }
+    config ?= { port: 9000 } // no-op, config is already not null
+    assertEquals(8080, config.port)
+
 ## Utility functions
 
 The following functions simplify nullable values processing and
@@ -186,9 +326,9 @@ Much like let, but it does not alter returned value:
     >>> void
 
 While it is not altering return value, the source object could be changed:
-
-    class Point(x,y)
-    val p = Point(1,2).also { it.x++ }
+also
+    class Point(var x: Int, var y: Int)
+    val p: Point = Point(1,2).also { it.x++ }
     assertEquals(p.x, 2)
     >>> void
 
@@ -196,12 +336,22 @@ While it is not altering return value, the source object could be changed:
 
 It works much like `also`, but is executed in the context of the source object:
 
-    class Point(x,y)
+    class Point(var x: Int, var y: Int)
     // see the difference: apply changes this to newly created Point:
-    val p = Point(1,2).apply { x++; y++ }
+    val p = Point(1,2).apply { this@Point.x++; this@Point.y++ }
     assertEquals(p, Point(2,3))
     >>> void
 
+## with
+
+Sets `this` to the first argument and executes the block. Returns the value returned by the block:
+
+    class Point(var x: Int, var y: Int)
+    val p = Point(1,2)
+    val sum = with(p) { x + y }
+    assertEquals(3, sum)
+    >>> void
+
 ## run
 
 Executes a block after it returning the value passed by the block. for example, can be used with elvis operator:
@@ -272,8 +422,6 @@ Reference quality and object equality example:
     assert( null == null)  // singletons
     assert( null === null)
     // but, for non-singletons:
-    assert( 5 == 5)
-    assert( 5 !== 5)
     assert( "foo" !== "foo" )
     >>> void
 
@@ -290,7 +438,7 @@ will be thrown:
     // WRONG! Exception will be thrown at next line:
     foo + "bar"
 
-Correct pattern is:
+The correct pattern is:
 
     foo = "foo"
     // now is OK:
@@ -306,8 +454,6 @@ Almost the same, using `val`:
     val foo = 1
     foo += 1 // this will throw exception
 
-# Constants
-
 Same as in kotlin:
 
     val HalfPi = π / 2
@@ -315,6 +461,163 @@ Same as in kotlin:
 Note using greek characters in identifiers! All letters allowed, but remember who might try to read your script, most
 likely will know some English, the rest is the pure uncertainty.
 
+# Types and inference
+
+Lyng uses Kotlin-style static types with inference. You can always write explicit types, but in most places the compiler
+can infer them from literals, defaults, and flow analysis.
+
+## Type annotations
+
+Use `:` to specify a type:
+
+    var x: Int = 10
+    val label: String = "count"
+    fun clamp(x: Int, min: Int, max: Int): Int { ... }
+
+`Object` is the top type. If you omit a type and there is no default value, the parameter is `Object` by default:
+
+    fun show(x) { println(x) }   // x is Object
+
+For nullable types, add `?`:
+
+    fun showMaybe(x: Object?) { ... }
+    fun parseInt(s: String?): Int? { ... }
+
+There is also a nullable shorthand for untyped parameters and constructor args: `x?` means `x: Object?`.
+It cannot be combined with an explicit type annotation.
+
+    class A(x?) { ... }     // x: Object?
+    fun f(x?) { x == null } // x: Object?
+
+Type aliases name type expressions and can be generic:
+
+    type Num = Int | Real
+    type Maybe<T> = T?
+
+Aliases expand to their underlying type expressions. See `docs/generics.md` for details.
+
+`void` is a singleton value of the class `Void`. `Void` can be used as an explicit return type:
+
+    fun log(msg): Void { println(msg); void }
+
+`Null` is the class of `null`. It is a singleton type and mostly useful for type inference results.
+
+For type expressions, you can check nullability directly:
+
+    T is nullable
+    T !is nullable
+
+This is especially useful in generic code and in `when` over a type parameter:
+
+    fun describe<T>(x: T): String = when (T) {
+        nullable -> "nullable"
+        else -> "non-null"
+    }
+
+## Type inference
+
+The compiler infers types from:
+
+- literals: `1` is `Int`, `1.0` is `Real`, `"s"` is `String`, `'c'` is `Char`
+- defaults: `fun f(x=1, name="n")` infers `x: Int`, `name: String`
+- assignments: `val x = call()` uses the return type of `call`
+- returns and branches: the result type of a block is the last expression, and if any branch is nullable,
+  the inferred type becomes nullable
+- numeric ops: `Int` and `Real` stay `Int` when both sides are `Int`, and promote to `Real` on mixed arithmetic
+
+Examples:
+
+    fun inc(x=0) = x + 1        // (Int)->Int
+    fun maybe(flag) { if(flag) 1 else null } // ()->Int?
+
+Function types are written as `(T1, T2, ...)->R`. You can include ellipsis in function *types* to
+express a variadic position:
+
+    var fmt: (String, Object...)->String
+    var f: (Int, Object..., String)->Real
+    var anyArgs: (...)->Int   // shorthand for (Object...)->Int
+
+Untyped locals are allowed, but their type is fixed on the first assignment:
+
+    var x
+    x = 1       // x becomes Int
+    x = "one"   // compile-time error
+
+    var y = null  // y is Object?
+    val z = null  // z is Null
+
+Empty list/map literals default to `List<Object>` and `Map<Object,Object>` until a more specific type is known:
+
+    val xs = []             // List<Object>
+    val ys: List<Int> = []  // List<Int>
+
+Map literals infer key/value types from entries; named keys are `String`. See `docs/generics.md` for details.
+
+## Flow analysis
+
+Lyng uses flow analysis to narrow types inside branches:
+
+    fun len(x: String?): Int {
+        if( x == null ) return 0
+        // x is String (non-null) in this branch
+        return x.length
+    }
+
+`is` checks and `when` branches also narrow types:
+
+    fun kind(x: Object) {
+        if( x is Int ) return "int"
+        if( x is String ) return "string"
+        return "other"
+    }
+
+Narrowing is local to the branch; after the branch, the original type is restored.
+
+## Casts and unknown types
+
+Use `as` for explicit casts. The compiler inserts casts only when it can be valid and necessary. If a cast fails at
+runtime, it throws `ClassCastException`. If the value is nullable, `as T` implies a non-null assertion.
+
+Member access is resolved at compile time. Only members of `Object` are available on unknown types; non-Object members
+require an explicit cast:
+
+    fun f(x) {             // x is Object
+        x.toString()       // ok (Object member)
+        x.size()           // compile-time error
+        (x as List).size() // ok
+    }
+
+This avoids runtime name-resolution fallbacks; all symbols must be known at compile time.
+
+## Generics and bounds
+
+Generic parameters are declared with `<...>`:
+
+    fun id<T>(x: T): T = x
+    class Box<T>(val value: T)
+
+Bounds use `:` and can combine with `&` (intersection) and `|` (union):
+
+    fun sum<T: Int | Real>(x: T, y: T) = x + y
+    class Named<T: Iterable & Comparable>(val data: T)
+
+Type arguments are usually inferred from call sites:
+
+    val b = Box(10)     // Box<Int>
+    val s = id("ok")    // T is String
+
+See [Generics and type expressions](generics.md) for bounds, unions/intersections, and type-checking rules.
+
+## Variance
+
+Generic types are invariant by default, so `List<Int>` is not a `List<Object>`.
+Use declaration-site variance when you need it:
+
+    class Source<out T>(val value: T)
+    class Sink<in T> { fun accept(x: T) { ... } }
+
+`out` makes the type covariant (only produced), `in` makes it contravariant (only consumed).
+
 # Defining functions
 
     fun check(amount) {
@@ -356,14 +659,28 @@ There are default parameters in Lyng:
 It is possible to define also vararg using ellipsis:
 
     fun sum(args...) {
-        var result = args[0]
-        for( i in 1 ..< args.size ) result += args[i]
+        val list = args as List
+        var result = list[0]
+        for( i in 1 ..< list.size ) result += list[i]
     }
     sum(10,20,30)
     >>> 60
 
 See the [arguments reference](declaring_arguments.md) for more details.
 
+## Named arguments
+
+When calling functions, you can use named arguments with the colon syntax `name: value`. This is particularly useful when you have many parameters with default values.
+
+```lyng
+    fun test(a="foo", b="bar", c="bazz") { [a, b, c] }
+
+    assertEquals(["foo", "b", "bazz"], test(b: "b"))
+    assertEquals(["a", "bar", "c"], test("a", c: "c"))
+```
+
+**Note for Kotlin users:** Lyng uses `:` instead of `=` for named arguments at call sites. This is because in Lyng, `=` is an expression that returns the assigned value, and using it in an argument list would create ambiguity.
+
 ## Closures
 
 Each __block has an isolated context that can be accessed from closures__. For example:
@@ -437,14 +754,22 @@ one could be with ellipsis that means "the rest pf arguments as List":
     assert( { a, b...-> [a,...b] }(100, 1, 2, 3) == [100, 1, 2, 3]) 
     void
 
+Type-annotated lambdas can use variadic *function types* as well:
+
+    val f: (Int, Object..., String)->Real = { a, rest..., b -> 0.0 }
+    val anyArgs: (...)->Int = { -> 0 }
+
 ### Using lambda as the parameter
 
+See also: [Testing and Assertions](Testing.md)
+
     // note that fun returns its last calculated value,
     // in our case, result after in-place addition:
     fun mapValues(iterable, transform) {
         var result = []
         for( x in iterable ) result += transform(x)
     }
+    // loop variables are read-only inside the loop body
     assert( [11, 21, 31] == mapValues( [1,2,3], { it*10+1 }))
     >>> void
 
@@ -472,6 +797,7 @@ Lyng has built-in mutable array class `List` with simple literals:
 
 [List] is an implementation of the type `Array`, and through it `Collection` and [Iterable]. Please read [Iterable],
 many collection based methods are implemented there.
+For immutable list values, use `list.toImmutable()` and [ImmutableList].
 
 Lists can contain any type of objects, lists too:
 
@@ -480,7 +806,7 @@ Lists can contain any type of objects, lists too:
     assert( list is Array )     // general interface
     assert(list.size == 3)
     // second element is a list too:
-    assert(list[1].size == 2)
+    assert((list[1] as List).size == 2)
     >>> void
 
 Notice usage of indexing. You can use negative indexes to offset from the end of the list; see more in [Lists](List.md).
@@ -654,17 +980,68 @@ Set are unordered collection of unique elements, see [Set]. Sets are [Iterable]
     >>> void
 
 Please see [Set] for detailed description.
+For immutable set values, use `set.toImmutable()` and [ImmutableSet].
 
 # Maps
 
-Maps are unordered collection of key-value pairs, where keys are unique. See [Map] for details. Map also
-are [Iterable]:
+Maps are unordered collections of key-value pairs, where keys are unique. Maps are also [Iterable].
 
-    val m = Map( "foo" => 77, "bar" => "buzz" )
-    assertEquals( m["foo"], 77 )
+You can create them either with the classic constructor (still supported):
+
+    val old = Map( "foo" => 77, "bar" => "buzz" )
+    assertEquals( old["foo"], 77 )
     >>> void
 
-Please see [Map] reference for detailed description on using Maps.
+…or with map literals, which are often more convenient:
+
+    val x = 10
+    val y = 10
+    val m = { "a": 1, x: x * 2, y: }
+    // identifier keys become strings; `y:` is shorthand for y: y
+    assertEquals(1, m["a"])      // string-literal key
+    assertEquals(20, m["x"])     // identifier key
+    assertEquals(10, m["y"])     // shorthand
+    >>> void
+
+Map literals support trailing commas for nicer diffs:
+
+    val m2 = {
+        "a": 1,
+        b: 2,
+    }
+    assertEquals(1, m2["a"]) 
+    assertEquals(2, m2["b"]) 
+    >>> void
+
+You can spread other maps inside a literal with `...`. Items merge left-to-right and the rightmost value wins:
+
+    val base = { a: 1, b: 2 }
+    val merged = { a: 0, ...base, b: 3, c: 4 }
+    assertEquals(1, merged["a"])  // base overwrites a:0
+    assertEquals(3, merged["b"])  // literal overwrites spread
+    assertEquals(4, merged["c"])  // new key
+    >>> void
+
+Merging also works with `+` and `+=`, and you can combine maps and entries conveniently:
+
+    val m3 = { "a": 10 } + ("b" => 20)
+    assertEquals(10, m3["a"]) 
+    assertEquals(20, m3["b"]) 
+
+    var m4 = ("x" => 1) + ("y" => 2)      // entry + entry → Map
+    m4 += { z: 3 }                          // merge literal
+    assertEquals(1, m4["x"]) 
+    assertEquals(2, m4["y"]) 
+    assertEquals(3, m4["z"]) 
+    >>> void
+
+Notes:
+- Access keys with brackets: `m["key"]`. There is no `m.key` sugar.
+- Empty `{}` remains a block/lambda; use `Map()` to create an empty map.
+- When you need computed (expression) keys or non-string keys, use `Map(...)` constructor with entries, e.g. `Map( ("a" + "b") => 1 )`, then merge with a literal if needed: `{ base: } + (computedKey => 42)`.
+
+Please see the [Map] reference for a deeper guide.
+For immutable map values, use `map.toImmutable()` and [ImmutableMap].
 
 # Flow control operators
 
@@ -693,6 +1070,8 @@ Or, more neat:
 
 ## When
 
+See also: [Comprehensive guide to `when`](when.md)
+
 It is very much like the kotlin's:
 
     fun type(x) {
@@ -877,8 +1256,8 @@ ends normally, without breaks. It allows override loop result value, for example
 to not calculate it in every iteration. For example, consider this naive prime number
 test function (remember function return it's last expression result):
 
-    fun naive_is_prime(candidate) {
-        val x = if( candidate !is Int) candidate.toInt() else candidate
+    fun naive_is_prime(candidate: Int) {
+        val x = candidate
         var divisor = 1
         while( ++divisor < x/2 || divisor == 2 ) {
             if( x % divisor == 0 ) break false
@@ -953,8 +1332,9 @@ For loop are intended to traverse collections, and all other objects that suppor
 size and index access, like lists:
 
     var letters = 0
-    for( w in ["hello", "wolrd"]) {
-        letters += w.length
+    val words: List<String> = ["hello", "world"]
+    for( w in words) {
+        letters += (w as String).length
     }
     "total letters: "+letters
     >>> "total letters: 10"
@@ -1067,7 +1447,7 @@ The same with `--`:
     sum
     >>> 5050
 
-There are self-assigning version for operators too:
+There is a self-assigning version for operators too:
 
     var count = 100
     var sum = 0
@@ -1145,7 +1525,7 @@ than enum arrays, until `Lynon.encodeTyped` will be implemented.
     var result = null // here we will store the result
     >>> null
 
-# Integral data types
+# Built-in types
 
 | type   | description                     | literal samples     |
 |--------|---------------------------------|---------------------|
@@ -1155,6 +1535,7 @@ than enum arrays, until `Lynon.encodeTyped` will be implemented.
 | Char   | single unicode character        | `'S'`, `'\n'`       |
 | String | unicode string, no limits       | "hello" (see below) |
 | List   | mutable list                    | [1, "two", 3]       |
+| Object | top type for all values         |                     |
 | Void   | no value could exist, singleton | void                |
 | Null   | missing value, singleton        | null                |
 | Fn     | callable type                   |                     |
@@ -1174,18 +1555,21 @@ The type for the character objects is `Char`.
 | \t     | 0x07, tabulation      |
 | \\     | \ slash character     |
 | \"     | " double quote        |
+| \uXXXX | unicode code point    |
+
+Unicode escape form is exactly 4 hex digits, e.g. `"\u263A"` -> `☺`.
 
 Other `\c` combinations, where c is any char except mentioned above, are left intact, e.g.:
 
     val s = "\a"
-    assert(s[0] == '\')
+    assert(s[0] == '\\')
     assert(s[1] == 'a')
     >>> void
 
 same as:
 
     val s = "\\a"
-    assert(s[0] == '\')
+    assert(s[0] == '\\')
     assert(s[1] == 'a')
     >>> void
 
@@ -1200,6 +1584,9 @@ Are the same as in string literals with little difference:
 | \t     | 0x07, tabulation      |
 | \\     | \ slash character     |
 | \'     | ' apostrophe          |
+| \uXXXX | unicode code point    |
+
+For char literals, use `'\\'` to represent a single backslash character; `'\'` is invalid.
 
 ### Char instance members
 
@@ -1277,41 +1664,51 @@ Concatenation is a `+`: `"hello " + name` works as expected. No confusion. There
 
 Extraction:
 
-    "abcd42def"[ "\d+".re ].value
+    ("abcd42def"[ "\d+".re ] as RegexMatch).value
     >>> "42"
 
 Part match:
 
     assert( "abc foo def" =~ "f[oO]+".re )
-    assert( "foo" == $~.value )
+    assert( "foo" == ($~ as RegexMatch).value )
     >>> void
 
-Typical set of String functions includes:
+Repeating the fragment:
 
-| fun/prop           | description / notes                                        |
-|--------------------|------------------------------------------------------------|
-| lower()            | change case to unicode upper                               |
-| upper()            | change case to unicode lower                               |
-| trim()             | trim space chars from both ends                            |
-| startsWith(prefix) | true if starts with a prefix                               |
-| endsWith(prefix)   | true if ends with a prefix                                 |
-| take(n)            | get a new string from up to n first characters             |
-| takeLast(n)        | get a new string from up to n last characters              |
-| drop(n)            | get a new string dropping n first chars, or empty string   |
-| dropLast(n)        | get a new string dropping n last chars, or empty string    |
-| size               | size in characters like `length` because String is [Array] |
-| (args...)          | sprintf-like formatting, see [string formatting]           |
-| [index]            | character at index                                         | 
-| [Range]            | substring at range (2)                                     |
-| [Regex]            | find first match of regex, like [Regex.find] (2)           |
-| s1 + s2            | concatenation                                              |
-| s1 += s2           | self-modifying concatenation                               |
-| toReal()           | attempts to parse string as a Real value                   |
-| toInt()            | parse string to Int value                                  |
-| characters()       | create [List] of characters (1)                            |
-| encodeUtf8()       | returns [Buffer] with characters encoded to utf8           |
-| matches(re)        | matches the regular expression (2)                         |
-|                    |                                                            |
+    assertEquals("hellohello", "hello"*2)
+    assertEquals("", "hello"*0)
+    >>> void
+
+A typical set of String functions includes:
+
+| fun/prop             | description / notes                                        |
+|----------------------|------------------------------------------------------------|
+| lower(), lowercase() | change case to unicode upper                               |
+| upper(), uppercase() | change case to unicode lower                               |
+| trim()               | trim space chars from both ends                            |
+| isEmpty()            | true if string is empty                                    |
+| isNotEmpty()         | true if string is not empty                                |
+| isBlank()            | true if empty or contains only whitespace                  |
+| startsWith(prefix)   | true if starts with a prefix                               |
+| endsWith(prefix)     | true if ends with a prefix                                 |
+| last()               | get last character of a string or throw                    |
+| take(n)              | get a new string from up to n first characters             |
+| takeLast(n)          | get a new string from up to n last characters              |
+| drop(n)              | get a new string dropping n first chars, or empty string   |
+| dropLast(n)          | get a new string dropping n last chars, or empty string    |
+| size                 | size in characters like `length` because String is [Array] |
+| (args...)            | sprintf-like formatting, see [string formatting]           |
+| [index]              | character at index                                         | 
+| [Range]              | substring at range (2)                                     |
+| [Regex]              | find first match of regex, like [Regex.find] (2)           |
+| s1 + s2              | concatenation                                              |
+| s1 += s2             | self-modifying concatenation                               |
+| toReal()             | attempts to parse string as a Real value                   |
+| toInt()              | parse string to Int value                                  |
+| characters           | create [List] of characters (1)                            |
+| encodeUtf8()         | returns [Buffer] with characters encoded to utf8           |
+| matches(re)          | matches the regular expression (2)                         |
+|                      |                                                            |
 
 (1)
 : List is mutable therefore a new copy is created on each call.
@@ -1357,8 +1754,8 @@ See [math functions](math.md). Other general purpose functions are:
 | print(args...)                        | Open for overriding, it prints to stdout without newline.  |
 | flow {}                               | create flow sequence, see [parallelism]                    |
 | delay, launch, yield                  | see [parallelism]                                          |
-| cached(builder)                       | remembers builder() on first invocation and return it then |
-| let, also, apply, run                 | see above, flow controls                                   |
+| cached(builder)                       | [Lazy evaluation with `cached`](#lazy-evaluation-with-cached) |
+| let, also, apply, run, with       | see above, flow controls                                   |
 
 (1)
 : `fn` is optional lambda returning string message to add to exception string. 
@@ -1374,6 +1771,9 @@ Lambda avoid unnecessary execution if assertion is not failed. for example:
 | π                                   | See [math](math.md)          |
 
 [List]: List.md
+[ImmutableList]: ImmutableList.md
+
+[Testing]: Testing.md
 
 [Iterable]: Iterable.md
 
@@ -1383,13 +1783,15 @@ Lambda avoid unnecessary execution if assertion is not failed. for example:
 
 [Range]: Range.md
 
-[String]: development/String.md
+[String]: ../archived/development/String.md
 
 [string formatting]: https://github.com/sergeych/mp_stools?tab=readme-ov-file#sprintf-syntax-summary
 
 [Set]: Set.md
+[ImmutableSet]: ImmutableSet.md
 
 [Map]: Map.md
+[ImmutableMap]: ImmutableMap.md
 
 [Buffer]: Buffer.md
 
@@ -1403,6 +1805,50 @@ Lambda avoid unnecessary execution if assertion is not failed. for example:
 
 [Regex]: Regex.md
 
+## Lazy evaluation with `cached`
+
+Sometimes you have an expensive computation that you only want to perform if and when it is actually needed, and then remember (cache) the result for all future calls. Lyng provides the `cached(builder)` function for this purpose.
+
+It is extremely simple to use: you pass it a block (lambda) that performs the computation, and it returns a zero-argument function that manages the caching for you.
+
+### Basic Example
+
+```lyng
+val expensive = cached {
+    println("Performing expensive calculation...")
+    2 + 2
+}
+
+println(expensive()) // Prints "Performing expensive calculation...") then "4"
+println(expensive()) // Prints only "4" (result is cached)
+```
+
+### Benefits and Simplicity
+
+1.  **Lazy Execution:** The code inside the `cached` block doesn't run until you actually call the resulting function.
+2.  **Automatic State Management:** You don't need to manually check if a value has been computed or store it in a separate variable.
+3.  **Closures and Class Support:** `cached` works perfectly with closures. If you use it inside a class, it will correctly capture the instance variables, and each instance will have its own independent cache.
+
+### Use Case: Lazy Properties in Classes
+
+This is the most common use case for `cached`. It allows you to define expensive "fields" that are only computed if someone actually uses them:
+
+```lyng
+class User(val id: Int) {
+    // The details will be fetched only once, on demand
+    val details = cached {
+        println("Fetching details for user " + id)
+        // Db.query is a hypothetical example
+        Db.query("SELECT * FROM users WHERE id = " + id)
+    }
+}
+
+val u = User(101)
+// ... nothing happens yet ...
+val d = u.details() // Computation happens here
+val sameD = u.details() // Returns the same result immediately
+```
+
 ## Multiple Inheritance (quick start)
 
 Lyng supports multiple inheritance (MI) with simple, predictable rules. For a full reference see OOP notes, this is a quick, copy‑paste friendly overview.
@@ -1463,5 +1909,31 @@ assertEquals(null, (buzz as? Foo)?.runA())
 
 Notes:
 - Resolution order uses C3 MRO (active): deterministic, monotonic order suitable for diamonds and complex hierarchies. Example: for `class D() : B(), C()` where both `B()` and `C()` derive from `A()`, the C3 order is `D → B → C → A`. The first visible match wins.
-- `private` is visible only inside the declaring class; `protected` is visible from the declaring class and any of its transitive subclasses. Qualification (`this@Type`) or casts do not bypass visibility.
+- `private` is visible only inside the declaring class; `protected` is visible from the declaring class and its subclasses. Additionally, ancestors can access protected members of descendants if they override a member known to the ancestor. Qualification (`this@Type`) or casts do not bypass visibility.
 - Safe‑call `?.` works with `as?` for optional dispatch.
+
+## Extension members
+
+You can add new methods and properties to existing classes without modifying them.
+
+### Extension functions
+
+    fun String.shout() = this.upper() + "!!!"
+    "hello".shout()
+    >>> "HELLO!!!"
+
+### Extension properties
+
+    val Int.isEven get() = this % 2 == 0
+    4.isEven
+    >>> true
+
+Example with custom accessors:
+
+    val String.firstChar get() = this[0]
+    "abc".firstChar
+    >>> 'a'
+
+Extension members are **scope-isolated**: they are visible only in the scope where they are defined and its children. This prevents name collisions and improves security.
+
+To get details on OOP in Lyng, see [OOP notes](OOP.md).

docs/wasm_generation_bug.md

@@ -0,0 +1,27 @@
+# Wasm generation hang in wasmJs browser tests
+
+## Summary
+The wasmJs browser test runner hung after commit 5f819dc. The root cause was invalid WebAssembly generated by the Kotlin/Wasm backend when certain compiler paths emitted suspend lambdas for `Statement` execution. The invalid module failed to instantiate in the browser, and Karma kept the browser connected but never ran tests.
+
+## Symptoms
+- `:lynglib:wasmJsBrowserTest` hangs indefinitely in ChromeHeadless.
+- `:lynglib:wasmJsNodeTest` fails with a WebAssembly compile error similar to:
+  - `struct.set expected type (ref null XXXX), found global.get of type (ref null YYYY)`
+- The failing function name in the wasm name section looks like:
+  - `net.sergeych.lyng.$invokeCOROUTINE$.doResume`
+
+## Root cause
+The delegation/var-declaration changes introduced compiler-generated suspend lambdas inside `Statement` construction (e.g., `statement { ... }` wrappers). Kotlin/Wasm generates extra coroutine state for those suspend lambdas, which in this case produced invalid wasm IR (mismatched GC reference types). The browser loader then waits forever because the module fails to instantiate.
+
+## Fix
+Avoid suspend-lambda `Statement` construction in compiler code paths. Replace `statement { ... }` and other anonymous suspend lambdas with explicit `object : Statement()` implementations and move logic into `override suspend fun execute(...)`. This keeps the resulting wasm IR valid while preserving behavior.
+
+## Where it was fixed
+- `lynglib/src/commonMain/kotlin/net/sergeych/lyng/Compiler.kt`
+- `lynglib/src/commonMain/kotlin/net/sergeych/lyng/Scope.kt`
+
+## Verification
+- `./gradlew :lynglib:wasmJsNodeTest --info`
+- `./gradlew :lynglib:wasmJsBrowserTest --info`
+
+Both tests finish quickly after the change.

docs/whats_new.md

@@ -0,0 +1,254 @@
+# What's New in Lyng
+
+This document highlights the latest additions and improvements to the Lyng language and its ecosystem.
+For a programmer-focused migration summary, see `docs/whats_new_1_5.md`.
+
+## Language Features
+
+### Class Properties with Accessors
+Classes now support properties with custom `get()` and `set()` accessors. Properties in Lyng do **not** have automatic backing fields; they are pure accessors.
+
+```lyng
+class Person(private var _age: Int) {
+    // Read-only property
+    val ageCategory get() = if (_age < 18) "Minor" else "Adult"
+
+    // Read-write property
+    var age: Int
+        get() = _age
+        set(v) {
+            if (v >= 0) _age = v
+        }
+}
+```
+
+### Private and Protected Setters
+You can now restrict the visibility of a property's or field's setter using `private set` or `protected set`. This allows members to be publicly readable but only writable from within the declaring class or its subclasses.
+
+### Refined Protected Visibility
+Ancestor classes can now access `protected` members of their descendants if it is an override of a member known to the ancestor. This enables base classes to call protected methods that are implemented or overridden in subclasses.
+
+```lyng
+class Counter {
+    var count = 0
+        private set  // Field with private setter
+        
+    fun increment() { count++ }
+}
+
+class AdvancedCounter : Counter {
+    var totalOperations = 0
+        protected set // Settable here and in further subclasses
+}
+
+let c = Counter()
+c.increment() // OK
+// c.count = 10 // Error: setter is private
+```
+
+### Late-initialized `val` Fields
+`val` fields in classes can be declared without an immediate initializer, provided they are assigned exactly once. If accessed before initialization, they hold the special `Unset` singleton.
+
+```lyng
+class Service {
+    val logger
+    
+    fun check() {
+        if (logger == Unset) println("Not initialized yet")
+    }
+
+    init {
+        logger = Logger("Service")
+    }
+}
+```
+
+### Named Arguments and Named Splats
+Function calls now support named arguments using the `name: value` syntax. If the variable name matches the parameter name, you can use the `name:` shorthand.
+
+```lyng
+fun greet(name, greeting = "Hello") {
+    println("$greeting, $name!")
+}
+
+val name = "Alice"
+greet(name:)                  // Shorthand for greet(name: name)
+greet(greeting: "Hi", name: "Bob")
+
+let params = { name: "Charlie", greeting: "Hey")
+greet(...params)              // Named splat expansion
+```
+
+### Multiple Inheritance (MI)
+Lyng now supports multiple inheritance using the C3 Method Resolution Order (MRO). Use `this@Type` or casts for disambiguation.
+
+```lyng
+class A { fun foo() = "A" }
+class B { fun foo() = "B" }
+
+class Derived : A, B {
+    fun test() {
+        println(foo())              // Resolves to A.foo (leftmost)
+        println(this@B.foo())       // Qualified dispatch to B.foo
+    }
+}
+
+let d = Derived()
+println((d as B).foo())             // Disambiguation via cast
+```
+
+### Singleton Objects
+Singleton objects are declared using the `object` keyword. They provide a convenient way to define a class and its single instance in one go.
+
+```lyng
+object Config {
+    val version = "1.5.0-SNAPSHOT"
+    fun show() = println("Config version: " + version)
+}
+
+Config.show()
+```
+
+### Nested Declarations and Lifted Enums
+You can now declare classes, objects, enums, and type aliases inside another class. These nested declarations live in the class namespace (no outer instance capture) and are accessed with a qualifier.
+
+```lyng
+class A {
+    class B(x?)
+    object Inner { val foo = "bar" }
+    enum E* { One, Two }
+}
+
+val ab = A.B()
+assertEquals(ab.x, null)
+assertEquals(A.Inner.foo, "bar")
+assertEquals(A.One, A.E.One)
+```
+
+The `*` on `enum E*` lifts entries into the enclosing class namespace (compile-time error on ambiguity).
+
+### Object Expressions
+You can now create anonymous objects that inherit from classes or interfaces using the `object : Base { ... }` syntax. These expressions capture their lexical scope and support multiple inheritance.
+
+```lyng
+val worker = object : Runnable {
+    override fun run() = println("Working...")
+}
+
+val x = object : Base(arg1), Interface1 {
+    val property = 42
+    override fun method() = this@object.property * 2
+}
+```
+
+Use `this@object` to refer to the innermost anonymous object instance when `this` is rebound.
+
+### Unified Delegation Model
+A powerful new delegation system allows `val`, `var`, and `fun` members to delegate their logic to other objects using the `by` keyword.
+
+```lyng
+// Property delegation
+val lazyValue by lazy { "expensive" }
+
+// Function delegation
+fun remoteAction by myProxy
+
+// Observable properties
+var name by Observable("initial") { n, old, new -> 
+    println("Changed!") 
+}
+```
+
+The system features a unified interface (`getValue`, `setValue`, `invoke`) and a `bind` hook for initialization-time validation and configuration. See the [Delegation Guide](delegation.md) for more.
+
+### User-Defined Exception Classes
+You can now create custom exception types by inheriting from the built-in `Exception` class. Custom exceptions are real classes that can have their own fields and methods, and they work seamlessly with `throw` and `try-catch` blocks.
+
+```lyng
+class ValidationException(val field, m) : Exception(m)
+
+try {
+    throw ValidationException("email", "Invalid format")
+}
+catch(e: ValidationException) {
+    println("Error in " + e.field + ": " + e.message)
+}
+```
+
+### Assign-if-null Operator (`?=`)
+The new `?=` operator provides a concise way to assign a value only if the target is `null`. It is especially useful for setting default values or lazy initialization.
+
+```lyng
+var x = null
+x ?= 42          // x is now 42
+x ?= 100         // x remains 42 (not null)
+
+// Works with properties and index access
+config.port ?= 8080
+settings["theme"] ?= "dark"
+```
+
+The operator returns the final value of the receiver (the original value if it was not `null`, or the new value if the assignment occurred).
+
+### Transient Attribute (`@Transient`)
+The `@Transient` attribute can now be applied to class fields, constructor parameters, and static fields to exclude them from serialization.
+
+```lyng
+class MyData(@Transient val tempSecret, val publicData) {
+    @Transient var cachedValue = 0
+    var persistentValue = 42
+}
+```
+
+Key features:
+- **Serialization**: Transient members are omitted from both Lynon binary streams and JSON output.
+- **Structural Equality**: Transient fields are automatically ignored during `==` equality checks.
+- **Deserialization**: Transient constructor parameters with default values are correctly restored to those defaults upon restoration.
+
+### Value Clamping (`clamp`)
+A new `clamp()` function has been added to the standard library to limit a value within a specified range. It is available as both a global function and an extension method on all objects.
+
+```lyng
+// Global function
+clamp(15, 0..10)    // returns 10
+clamp(-5, 0..10)   // returns 0
+
+// Extension method
+val x = 15
+x.clamp(0..10)      // returns 10
+
+// Exclusive and open-ended ranges
+15.clamp(0..<10)    // returns 9
+15.clamp(..10)      // returns 10
+-5.clamp(0..)       // returns 0
+```
+
+`clamp()` correctly handles inclusive (`..`) and exclusive (`..<`) ranges. For discrete types like `Int` and `Char`, clamping to an exclusive upper bound returns the previous value.
+
+## Tooling and Infrastructure
+
+### CLI: Formatting Command
+A new `fmt` subcommand has been added to the Lyng CLI.
+
+```bash
+lyng fmt MyFile.lyng             # Print formatted code to stdout
+lyng fmt --in-place MyFile.lyng  # Format file in-place
+lyng fmt --check MyFile.lyng     # Check if file needs formatting
+```
+
+### IDEA Plugin: Autocompletion
+Experimental lightweight autocompletion is now available in the IntelliJ plugin. It features type-aware member suggestions and inheritance-aware completion.
+
+You can enable it in **Settings | Lyng Formatter | Enable Lyng autocompletion**.
+
+### Kotlin API: Exception Handling
+The `Obj.getLyngExceptionMessageWithStackTrace()` extension method has been added to simplify retrieving detailed error information from Lyng exception objects in Kotlin. Additionally, `getLyngExceptionMessage()` and `raiseAsExecutionError()` now accept an optional `Scope`, making it easier to use them when a scope is not immediately available.
+
+### Kotlin API: Bridge Reflection and Class Binding (Preferred Extensions)
+Lyng now provides a public Kotlin reflection bridge and a Lyng‑first class binding workflow. This is the **preferred** way to write Kotlin extensions and library integrations:
+
+- **Bridge resolver**: explicit handles for values, vars, and callables with predictable lookup rules.
+- **Class bridge binding**: declare extern surfaces in Lyng (`extern` members, or members inside `extern class/object`) and bind the implementations in Kotlin before the first instance is created.
+- **Extern declaration rule**: `extern class` / `extern object` are declaration-only; all members in their bodies are implicitly extern.
+
+See **Embedding Lyng** for full samples and usage details.

docs/whats_new_1_3.md

@@ -0,0 +1,133 @@
+# What's New in Lyng 1.3 (vs 1.2.* / master)
+
+This is a programmer-focused summary of what changed since the 1.2.* line on `master`. It highlights new language and type-system features, runtime/IDE improvements, and how to migrate code safely.
+
+## Highlights
+
+- Generics are now a first-class part of the type system, with bounds, variance, unions, and intersections.
+- Type aliases and type-expression checks (`T1 is T2`, `A in T`) enable richer static modeling.
+- Nested declarations inside classes, plus lifted enum entries via `enum E*`.
+- Stepped ranges (`step`) including iterable open-ended and real ranges.
+- Runtime and compiler speedups: more bytecode coverage, direct slot access, call-site caching.
+
+## Language and type system
+
+### Generics, bounds, and variance
+
+You can declare generic functions/classes with `<...>`, restrict them with bounds, and control variance.
+
+```lyng
+fun id<T>(x: T): T = x
+class Box<out T>(val value: T)
+
+fun sum<T: Int | Real>(x: T, y: T) = x + y
+class Named<T: Iterable & Comparable>(val data: T)
+```
+
+### Type aliases and type expressions
+
+Type aliases can name any type expression, including unions and intersections.
+
+```lyng
+type Num = Int | Real
+type Maybe<T> = T?
+```
+
+Type expressions can be checked directly:
+
+```lyng
+fun f<T>(xs: List<T>) {
+    assert( T is Int | String | Bool ) // type-subset check
+    assert( Int in T )                 // same relation as `Int is T`
+}
+```
+
+Value checks remain `x is T`. Type expression equality uses `==` and is structural.
+
+### Nullable shorthand for parameters
+
+Untyped parameters and constructor args can use `x?` as shorthand for `x: Object?`:
+
+```lyng
+class A(x?) { ... }
+fun f(x?) { x == null }
+```
+
+### List/map literal inference
+
+The compiler now infers element and key/value types from literals and spreads. Mixed element types produce unions.
+
+```lyng
+val a = [1, 2, 3]             // List<Int>
+val b = [1, "two", true]      // List<Int | String | Bool>
+val m = { "a": 1, "b": "x" } // Map<String, Int | String>
+```
+
+### Compile-time member access only
+
+Member access is resolved at compile time. On unknown types, only `Object` members are visible; other members require an explicit cast.
+
+```lyng
+fun f(x) {          // x: Object
+    x.toString()    // ok
+    x.size()        // compile-time error
+    (x as List).size()
+}
+```
+
+This removes runtime name-resolution fallbacks and makes errors deterministic.
+
+### Nested declarations and lifted enums
+
+Classes, objects, enums, and type aliases can be declared inside another class and accessed by qualifier. Enums can lift entries into the outer namespace with `*`.
+
+```lyng
+class A {
+    class B(x?)
+    object Inner { val foo = "bar" }
+    type Alias = B
+    enum E* { One, Two }
+}
+
+val b = A.B()
+assertEquals(A.One, A.E.One)
+```
+
+### Stepped ranges
+
+Ranges now support `step`, and open-ended/real ranges are iterable only with an explicit step.
+
+```lyng
+(1..5 step 2).toList()      // [1,3,5]
+(0.0..1.0 step 0.25).toList() // [0,0.25,0.5,0.75,1.0]
+(0.. step 1).take(3).toList() // [0,1,2]
+```
+
+## Tooling and performance
+
+- Bytecode compiler/VM coverage expanded (loops, expressions, calls), improving execution speed and consistency.
+- Direct frame-slot access and scoped slot addressing reduce lookup overhead, including in closures.
+- Call-site caching and numeric fast paths reduce hot-loop overhead.
+- IDE tooling updated for the new type system and nested declarations; MiniAst-based completion work continues.
+
+## Migration guide (from 1.2.*)
+
+1) Replace dynamic member access on unknown types
+- If you relied on runtime name resolution, add explicit casts or annotate types so the compiler can resolve members.
+
+2) Adopt new type-system constructs where helpful
+- Consider `type` aliases for complex unions/intersections.
+- Prefer generic signatures over `Object` when the API is parametric.
+
+3) Update range iteration where needed
+- Use `step` for open-ended or real ranges you want to iterate.
+
+4) Nullable shorthand is optional
+- If you used untyped nullable params, you can keep `x` (Object) or switch to `x?` (Object?) for clarity.
+
+## References
+
+- `docs/generics.md`
+- `docs/Range.md`
+- `docs/OOP.md`
+- `docs/BytecodeSpec.md`

docs/whats_new_1_5.md

@@ -0,0 +1,145 @@
+# What's New in Lyng 1.5 (vs 1.3.* / master)
+
+This document summarizes the significant changes and new features introduced in the 1.5 development cycle.
+
+## Principal changes
+
+### JIT compiler and compile-time types and symbols.
+
+This major improvement gives the following big advantages:
+
+- **Blazing Fast execution**: several times faster! (three to six times speedup in different scenarios).
+- **Better IDE support**: autocompletion, early error detection, types check.
+- **Error safety**: all symbols and types are checked at bound at compile-time. Many errors are detected earlier. Also, no risk that external or caller code would shadow some internally used symbols (especially in closures and inheritance).
+
+In particular, it means no slow and flaky runtime lookups. Once compiled, code guarantees that it will always call the symbol known at compile-time; runtime name lookup though does not guarantee it and can be source of hard to trace bugs. 
+
+### New stable API to create Kotlin extensions
+
+The API is fixed and will be kept with further Lyng core changes. It is now the recommended way to write Lyng extensions in Kotlin. It is much simpler and more elegant than the internal one. See [Kotlin Bridge Binding](../notes/kotlin_bridge_binding.md).
+
+Extern declaration clarification:
+- `extern class` / `extern object` are pure extern surfaces.
+- Members inside them are implicitly extern (`extern` on a member is optional/redundant).
+- Lyng method/property bodies for these declarations should be implemented as extensions instead.
+
+### Smart types system
+
+- **Deep inference**: The compiler analyzes types of symbols along the execution path and in many cases eliminates unnecessary casts or type specifications.
+- **Union and intersection types**: `A & B`, `A | B`.
+- **Generics**: Generic types are first-class citizens with support for [bounds and variance](generics.md). Type params are erased by default and are reified only when needed (e.g., `T::class`, `T is ...`, `as T`, or in extern-facing APIs), which enables checks like `A in T` when `T` is reified.
+- **Inner classes and enums**: Full support for nested declarations, including [Enums with lifting](OOP.md#lifted-enum-entries).
+
+## Other highlights
+
+- **The `return` Statement**: Added support for local and non-local returns using labels.
+- **Abstract Classes and Interfaces**: Full support for `abstract` members and the `interface` keyword.
+- **Singleton Objects**: Define singletons using the `object` keyword or use anonymous object expressions.
+- **Multiple Inheritance**: Enhanced multi-inheritance with predictable [C3 MRO resolution](OOP.md#multiple-inheritance-and-mro).
+- **Unified Delegation**: Powerful delegation model for `val`, `var`, and `fun` members. See [Delegation](delegation.md).
+- **Class Properties with Accessors**: Define `val` and `var` properties with custom `get()` and `set()`.
+- **Restricted Setter Visibility**: Use `private set` and `protected set` on fields and properties.
+- **Late-initialized `val`**: Support for `val` fields that are initialized in `init` blocks or class bodies.
+- **Transient Members**: Use `@Transient` to exclude members from serialization and equality checks.
+- **Named Arguments and Splats**: Improved call-site readability with `name: value` and map-based splats.
+- **Refined Visibility**: Improved `protected` access and `closed` modifier for better encapsulation.
+
+## Language Features
+
+### The `return` Statement
+You can now exit from the innermost enclosing callable (function or lambda) using `return`. Lyng also supports non-local returns to outer scopes using labels. See [Return Statement](return_statement.md).
+
+```lyng
+fun findFirst<T>(list: Iterable<T>, predicate: (T)->Bool): T? {
+    list.forEach {
+        if (predicate(it)) return@findFirst it
+    }
+    null
+}
+```
+
+### Abstract Classes and Interfaces
+Lyng now supports the `abstract` modifier for classes and their members. `interface` is introduced as a synonym for `abstract class`, allowing for rich multi-inheritance patterns.
+
+```lyng
+interface Shape {
+    abstract val area: Real
+    fun describe() = "Area: %g"(area)
+}
+
+class Circle(val radius: Real) : Shape {
+    override val area get = Math.PI * radius * radius
+}
+```
+
+### Class Properties with Accessors
+Properties can now have custom getters and setters. They do not have automatic backing fields, making them perfect for computed values or delegation.
+
+```lyng
+class Rectangle(var width: Real, var height: Real) {
+    val area: Real get() = width * height
+    
+    var squareSize: Real
+        get() = area
+        set(v) {
+            width = sqrt(v)
+            height = width
+        }
+}
+```
+
+### Singleton Objects
+Declare singletons or anonymous objects easily.
+
+```lyng
+object Database {
+    val connection = "connected"
+}
+
+val runner = object : Runnable {
+    override fun run() = println("Running!")
+}
+```
+
+### Named Arguments and Named Splats
+Improve call-site clarity by specifying argument names. You can also expand a Map into named arguments using the splat operator.
+
+```lyng
+fun configure(timeout: Int, retry: Int = 3) { ... }
+
+configure(timeout: 5000, retry: 5)
+val options = Map("timeout": 1000, "retry": 1)
+configure(...options)
+```
+
+### Modern Operators
+The `?=` operator allows for concise "assign if null" logic.
+
+```lyng
+var cache: Map? = null
+cache ?= Map("status": "ok") // Only assigns if cache is null
+```
+
+## Tooling and IDE
+
+- **IDEA Plugin**: Significant improvements to autocompletion, documentation tooltips, and natural language support (Grazie integration).
+- **CLI**: The `lyng fmt` command is now a first-class tool for formatting code with various options like `--check` and `--in-place`.
+- **Performance**: Ongoing optimizations in the bytecode VM and compiler for faster execution and smaller footprint.
+
+## Standard Library
+- **`with(self, block)`**: Scoped execution with a dedicated `self`.
+- **`clamp(value, min, max)`**: Easily restrict values to a range.
+
+## Migration Guide (from 1.3.*)
+
+1. **Check Visibility**: Refined `protected` and `private` rules may catch previously undetected invalid accesses.
+2. **Override Keyword**: Ensure all members that override ancestor declarations are marked with the `override` keyword (now mandatory).
+3. **Return in Shorthand**: Remember that `return` is forbidden in `=` shorthand functions; use block syntax if you need early exit.
+4. **Empty Map Literals**: Use `Map()` or `{:}` for empty maps, as `{}` is now strictly a block/lambda.
+
+## References
+- [Object Oriented Programming](OOP.md)
+- [Generics](generics.md)
+- [Return Statement](return_statement.md)
+- [Delegation](delegation.md)
+- [Tutorial](tutorial.md)

docs/when.md

@@ -0,0 +1,241 @@
+# The `when` statement (expression)
+
+[//]: # (topMenu)
+
+Lyng provides a concise multi-branch selection with `when`, heavily inspired by Kotlin. In Lyng, `when` is an expression: it evaluates to a value. If the selected branch contains no value (e.g., it ends with `void` or calls a void function like `println`), the whole `when` expression evaluates to `void`.
+
+Currently, Lyng implements the "subject" form: `when(value) { ... }`. The subject-less form `when { condition -> ... }` is not implemented yet.
+
+## Quick examples
+
+    val r1 = when("a") {
+        "a" -> "ok"
+        else -> "nope"
+    }
+    assertEquals("ok", r1)
+    
+    val r2 = when(5) {
+        3 -> "no"
+        4 -> "no"
+        else -> "five"
+    }
+    assertEquals("five", r2)
+    
+    val r3 = when(5) {
+        3 -> "no"
+        4 -> "no"
+    }
+    // no matching case and no else → `void`
+    assert(r3 == void)
+    >>> void
+
+## Syntax
+
+    when(subject) {
+        condition1 [, condition2, ...] -> resultExpressionOrBlock
+        conditionN -> result
+        else -> fallback
+    }
+
+- Commas group multiple conditions for one branch.
+- First matching branch wins; there is no fall‑through.
+- `else` is optional. If omitted and nothing matches, the result is `void`.
+
+## Matching rules (conditions)
+
+Within `when(subject)`, each condition is evaluated against the already evaluated `subject`. Lyng supports:
+
+1) Equality match (default)
+- Any expression value can be used as a condition. It matches if it is equal to `subject`.
+- Equality relies on Lyng’s comparison (`compareTo(...) == 0`). For user types, implement comparison accordingly.
+
+    when(x) {
+        0 -> "zero"
+        "EUR" -> "currency"
+    }
+    >>> void
+
+2) Type checks: `is` and `!is`
+- Check whether the subject is an instance of a class.
+- Works with built‑in classes and user classes.
+
+    fun typeOf(x) {
+        when(x) {
+            is Real, is Int -> "number"
+            is String -> "string"
+            else -> "other"
+        }
+    }
+    assertEquals("number", typeOf(5))
+    assertEquals("string", typeOf("hi"))
+    >>> void
+
+3) Containment checks: `in` and `!in`
+- `in container` matches if `container.contains(subject)` is true.
+- `!in container` matches if `contains(subject)` is false.
+- Any object that provides `contains(item)` can act as a container.
+
+Common containers:
+- Ranges (e.g., `'a'..'z'`, `1..10`, `1..<10`, `..5`, `5..`)
+- Lists, Sets, Arrays, Buffers
+- Strings (character or substring containment)
+
+Examples:
+
+    when('e') {
+        in 'a'..'c' -> "small"
+        in 'a'..'z' -> "letter"
+        else -> "other"
+    }
+    >>> "letter"
+    
+    when(5) {
+        in [1,2,3,4,6] -> "no"
+        in [7,0,9] -> "no"
+        else -> "ok"
+    }
+    >>> "ok"
+    
+    when(5) {
+        in [1,2,3,4,6] -> "no"
+        in [7,0,9] -> "no"
+        in [-1,5,11] -> "yes"
+        else -> "no"
+    }
+    >>> "yes"
+    
+    when(5) {
+        !in [1,2,3,4,6,5] -> "no"
+        !in [7,0,9,5] -> "no"
+        !in [-1,15,11] -> "ok"
+        else -> "no"
+    }
+    >>> "ok"
+    
+    // String containment
+    "foo" in "foobar"   // true (substring)
+    'o' in "foobar"      // true (character)
+    >>> true
+
+Notes on mixed String/Char ranges:
+- Prefer character ranges for characters: `'a'..'z'`.
+- `"a".."z"` is a String range and may not behave as you expect with `Char` subjects.
+
+    assert( "more" in "a".."z")
+    assert( 'x' !in "a".."z")  // Char vs String range: often not what you want
+    assert( 'x' in 'a'..'z')     // OK
+    assert( "x" !in 'a'..'z')   // String in Char range: likely not intended
+    >>> void
+
+## Grouping multiple conditions with commas
+
+You can group values and/or `is`/`in` checks for a single result:
+
+    fun classify(x) {
+        when(x) {
+            "42", 42 -> "answer"
+            is Real, is Int -> "number"
+            in ['@', '#', '^'] -> "punct1"
+            in "*&.," -> "punct2"
+            else -> "unknown"
+        }
+    }
+    assertEquals("number", classify(π/2))
+    assertEquals("answer", classify(42))
+    assertEquals("answer", classify("42"))
+    >>> void
+
+## Return value and blocks
+
+- `when` returns the value of the matched branch result expression/block.
+- Branch bodies can be single expressions or blocks `{ ... }`.
+- If a matched branch produces `void` (e.g., only prints), the `when` result is `void`.
+
+    val res = when(2) {
+        1 -> 10
+        2 -> { println("two"); 20 }
+        else -> 0
+    }
+    assertEquals(20, res)
+    >>> void
+
+## Else branch
+
+- Optional but recommended when non‑exhaustive.
+- If omitted and nothing matches, `when` result is `void` (see r3 in the Quick examples).
+- Only one `else` is allowed.
+
+## Subject‑less `when`
+
+The Kotlin‑style subject‑less form `when { condition -> ... }` is not implemented yet in Lyng. Use `if/else` chains or structure your checks around a subject with `when(subject) { ... }`.
+
+## Extending `when` for your own types
+
+### Equality matches
+- Equality checks in `when(subject)` use Lyng comparison (`compareTo` semantics under the hood). For your own Lyng classes, implement comparison appropriately so that `subject == value` works as intended.
+
+### `in` / `!in` containment
+- Provide a `contains(item)` method on your class to participate in `in` conditions.
+- Example: a custom `Box` that contains one specific item:
+
+    class Box(val item)
+    fun Box.contains(x) { x == item }
+    
+    val b = Box(10)
+    when(10) { in b -> "hit" }
+    >>> "hit"
+
+Any built‑in collection (`List`, `Set`, `Array`), `Range`, `Buffer`, and other containers already implement `contains`.
+
+### Type checks (`is` / `!is`)
+- Every value has a `::class` that yields its Lyng class object, e.g. `[1,2,3]::class` → `List`.
+- `is ClassName` in `when` uses Lyng’s class hierarchy. Ensure your class is declared and can be referenced by name.
+
+    []::class == List
+    >>> true
+    
+    fun f(x) { when(x) { is List -> "list" else -> "other" } }
+    assertEquals("list", f([1]))
+    >>> void
+
+## Kotlin‑backed classes (embedding)
+
+When embedding Lyng in Kotlin, you may expose Kotlin‑backed objects and classes. Interactions inside `when` work as follows:
+- `is` checks use the Lyng class object you expose for your Kotlin type. Ensure your exposed class participates in the Lyng class hierarchy (see Embedding docs).
+- `in` checks call `contains(subject)`; if your Kotlin‑backed object wants to support `in`, expose a `contains(item)` method (mapped to Lyng) or implement the corresponding Lyng container wrapper.
+- Equality follows Lyng comparison rules. Ensure your Kotlin‑backed object’s Lyng adapter implements equality/compare correctly.
+
+For details on exposing classes/methods from Kotlin, see: [Embedding Lyng in your Kotlin project](embedding.md).
+
+## Gotchas and tips
+
+- First match wins; there is no fall‑through. Order branches carefully.
+- Group related conditions with commas for readability and performance (a single branch evaluation).
+- Prefer character ranges for character tests; avoid mixing `String` and `Char` ranges.
+- If you rely on `in`, check that your container implements `contains(item)`.
+- Remember: `when` is an expression — you can assign its result to a variable or return it from a function.
+
+## Additional examples
+
+    fun label(ch) {
+        when(ch) {
+            in '0'..'9' -> "digit"
+            in 'a'..'z', in 'A'..'Z' -> "letter"
+            '$' -> "dollar"
+            else -> "other"
+        }
+    }
+    assertEquals("digit", label('3'))
+    assertEquals("dollar", label('$'))
+    >>> void
+
+    fun normalize(x) {
+        when(x) {
+            is Int -> x
+            is Real -> x.round()
+            else -> 0
+        }
+    }
+    assertEquals(12, normalize(12))
+    assertEquals(3,  normalize(2.6))
+    >>> void

editors/lyng-textmate/README.md

@@ -0,0 +1,68 @@
+Lyng TextMate grammar
+======================
+
+This folder contains a TextMate grammar for the Lyng language so you can get syntax highlighting quickly in:
+
+- JetBrains IDEs (IntelliJ IDEA, Fleet, etc.) via “TextMate Bundles”
+- VS Code (via “Install from VSIX” or by adding as an extension folder)
+
+Files
+-----
+- `package.json` — VS Code–style wrapper that JetBrains IDEs can import as a TextMate bundle.
+- `syntaxes/lyng.tmLanguage.json` — the grammar. It highlights:
+  - Line and block comments (`//`, `/* */`)
+  - Shebang line at file start (`#!...`)
+  - Strings: single and double quotes with escapes
+  - Char literals `'x'` with escapes
+  - Numbers: decimal with underscores and exponents, and hex (`0x...`)
+  - Keywords (control and declarations), boolean operator words (`and`, `or`, `not`, `in`, `is`, `as`, `as?`)
+  - Composite textual operators: `not in`, `not is`
+  - Constants: `true`, `false`, `null`, `this`
+  - Annotations: `@name` (Unicode identifiers supported)
+  - Labels: `name:` (Unicode identifiers supported)
+  - Declarations: highlights declared names in `fun|fn name`, `class|enum|interface Name`, `val|var name`
+  - Types: built-ins (`Int|Real|String|Bool|Char|Regex`) and Capitalized identifiers (heuristic)
+  - Operators including ranges (`..`, `..<`, `...`), null-safe (`?.`, `?[`, `?(`, `?{`, `?:`, `??`), arrows (`->`, `=>`, `::`), match operators (`=~`, `!~`), bitwise, arithmetic, etc.
+  - Shuttle operator `<=>`
+  - Division operator `/` (note: Lyng has no regex literal syntax; `/` is always division)
+  - Named arguments at call sites `name: value` (the `name` part is highlighted as `variable.parameter.named.lyng` and the `:` as punctuation). The rule is anchored to `(` or `,` and excludes `::` to avoid conflicts.
+
+Install in IntelliJ IDEA (and other JetBrains IDEs)
+---------------------------------------------------
+1. Open Settings / Preferences → Editor → TextMate Bundles.
+2. Click “+” and select this folder `editors/lyng-textmate/` (the folder that contains `package.json`).
+3. Ensure `*.lyng` is associated with the Lyng grammar (IntelliJ usually picks this up from `fileTypes`).
+4. Optional: customize colors with Settings → Editor → Color Scheme → TextMate.
+
+Enable Markdown code-fence highlighting in IntelliJ
+--------------------------------------------------
+1. Settings / Preferences → Languages & Frameworks → Markdown → Code style → Code fences → Languages.
+2. Add mapping: language id `lyng` → “Lyng (TextMate)”.
+3. Now blocks like
+   ```
+   ```lyng
+   // Lyng code here
+   ```
+   ```
+   will be highlighted.
+
+Install in VS Code
+------------------
+Fastest local install without packaging:
+1. Copy or symlink this folder somewhere stable (or keep it in your workspace).
+2. Use “Developer: Install Extension from Location…” (Insiders) or package with `vsce package` and install the resulting `.vsix`.
+3. VS Code will auto-associate `*.lyng` via this extension; if needed, check File Associations.
+
+Notes and limitations
+---------------------
+- Type highlighting is heuristic (Capitalized identifiers). The IntelliJ plugin will use language semantics and avoid false positives.
+- If your language adds or changes tokens, please update patterns in `lyng.tmLanguage.json`. The Kotlin sources in `lynglib/src/commonMain/kotlin/net/sergeych/lyng/highlight/` are a good reference for token kinds.
+- Labels `name:` at statement level remain supported and are kept distinct from named call arguments by context. The grammar prefers named-argument matching when a `name:` appears right after `(` or `,`.
+
+Lyng specifics
+--------------
+- There are no regex literal tokens in Lyng at the moment; the slash character `/` is always treated as the division operator. The grammar intentionally does not define a `/.../` regex rule to avoid mis-highlighting lines like `a / b`.
+
+Contributing
+------------
+Pull requests to refine patterns and add tests/samples are welcome. You can place test snippets in `sample_texts/` and visually verify.

editors/lyng-textmate/package.json

@@ -0,0 +1,25 @@
+{
+  "name": "lyng-textmate",
+  "displayName": "Lyng",
+  "description": "TextMate grammar for the Lyng language (for JetBrains IDEs via TextMate Bundles and VS Code).",
+  "version": "0.1.0",
+  "publisher": "lyng",
+  "license": "Apache-2.0",
+  "engines": { "vscode": "^1.0.0" },
+  "contributes": {
+    "languages": [
+      {
+        "id": "lyng",
+        "aliases": ["Lyng", "lyng"],
+        "extensions": [".lyng"]
+      }
+    ],
+    "grammars": [
+      {
+        "language": "lyng",
+        "scopeName": "source.lyng",
+        "path": "./syntaxes/lyng.tmLanguage.json"
+      }
+    ]
+  }
+}

editors/lyng-textmate/syntaxes/lyng.tmLanguage.json

@@ -0,0 +1,86 @@
+{
+  "$schema": "https://raw.githubusercontent.com/martinring/tmlanguage/master/tmlanguage.json",
+  "name": "Lyng",
+  "scopeName": "source.lyng",
+  "fileTypes": ["lyng"],
+  "patterns": [
+    { "include": "#shebang" },
+    { "include": "#comments" },
+    { "include": "#strings" },
+    { "include": "#char" },
+    { "include": "#numbers" },
+    { "include": "#declarations" },
+    { "include": "#keywords" },
+    { "include": "#constants" },
+    { "include": "#types" },
+    { "include": "#mapLiterals" },
+    { "include": "#namedArgs" },
+    { "include": "#annotations" },
+    { "include": "#labels" },
+    { "include": "#directives" },
+    { "include": "#operators" },
+    { "include": "#punctuation" }
+  ],
+  "repository": {
+    "shebang": { "patterns": [ { "name": "comment.line.shebang.lyng", "match": "^#!.*$" } ] },
+    "comments": {
+      "patterns": [
+        { "name": "comment.line.double-slash.lyng", "match": "//.*$" },
+        { "name": "comment.block.lyng", "begin": "/\\*", "end": "\\*/" }
+      ]
+    },
+    "strings": {
+      "patterns": [
+        { "name": "string.quoted.double.lyng", "begin": "\"", "end": "\"", "patterns": [ { "match": "\\\\.", "name": "constant.character.escape.lyng" } ] },
+        { "name": "string.quoted.single.lyng", "begin": "'", "end": "'", "patterns": [ { "match": "\\\\.", "name": "constant.character.escape.lyng" } ] }
+      ]
+    },
+    "char": { "patterns": [ { "name": "constant.character.lyng", "match": "'(?:[^\\\\']|\\\\.)'" } ] },
+    "numbers": {
+      "patterns": [
+        { "name": "constant.numeric.hex.lyng", "match": "0x[0-9A-Fa-f_]+" },
+        { "name": "constant.numeric.decimal.lyng", "match": "(?<![A-Za-z_])(?:[0-9][0-9_]*)\\.(?:[0-9_]+)(?:[eE][+-]?[0-9_]+)?|(?<![A-Za-z_])(?:[0-9][0-9_]*)(?:[eE][+-]?[0-9_]+)?" }
+      ]
+    },
+    "annotations": { "patterns": [ { "name": "entity.name.label.at.lyng", "match": "@[\\p{L}_][\\p{L}\\p{N}_]*" } ] },
+    "mapLiterals": {
+      "patterns": [
+        {
+          "name": "meta.map.entry.lyng",
+          "match": "(?:(?<=\\{|,))\\s*(\"[^\"]*\"|[\\p{L}_][\\p{L}\\p{N}_]*)\\s*(:)(?!:)",
+          "captures": {
+            "1": { "name": "variable.other.property.key.lyng" },
+            "2": { "name": "punctuation.separator.colon.lyng" }
+          }
+        },
+        {
+          "name": "meta.map.spread.lyng",
+          "match": "(?:(?<=\\{|,))\\s*(\\.\\.\\.)",
+          "captures": {
+            "1": { "name": "keyword.operator.spread.lyng" }
+          }
+        }
+      ]
+    },
+    "namedArgs": {
+      "patterns": [
+        {
+          "name": "meta.argument.named.lyng",
+          "match": "(?:(?<=\\()|(?<=,))\\s*([\\p{L}_][\\p{L}\\p{N}_]*)\\s*(:)(?!:)",
+          "captures": {
+            "1": { "name": "variable.parameter.named.lyng" },
+            "2": { "name": "punctuation.separator.colon.lyng" }
+          }
+        }
+      ]
+    },
+    "labels": { "patterns": [ { "name": "entity.name.label.lyng", "match": "[\\p{L}_][\\p{L}\\p{N}_]*@" } ] },
+    "directives": { "patterns": [ { "name": "meta.directive.lyng", "match": "^\\s*#[_A-Za-z][_A-Za-z0-9]*" } ] },
+    "declarations": { "patterns": [ { "name": "meta.function.declaration.lyng", "match": "\\b(fun|fn)\\s+(?:([\\p{L}_][\\p{L}\\p{N}_]*)\\.)?([\\p{L}_][\\p{L}\\p{N}_]*)", "captures": { "1": { "name": "keyword.declaration.lyng" }, "2": { "name": "entity.name.type.lyng" }, "3": { "name": "entity.name.function.lyng" } } }, { "name": "meta.type.declaration.lyng", "match": "\\b(?:class|enum|interface|object)(?:\\s+([\\p{L}_][\\p{L}\\p{N}_]*))?", "captures": { "1": { "name": "entity.name.type.lyng" } } }, { "name": "meta.variable.declaration.lyng", "match": "\\b(val|var)\\s+(?:([\\p{L}_][\\p{L}\\p{N}_]*)\\.)?([\\p{L}_][\\p{L}\\p{N}_]*)", "captures": { "1": { "name": "keyword.declaration.lyng" }, "2": { "name": "entity.name.type.lyng" }, "3": { "name": "variable.other.declaration.lyng" } } } ] },
+    "keywords": { "patterns": [ { "name": "keyword.control.lyng", "match": "\\b(?:if|else|when|while|do|for|try|catch|finally|throw|return|break|continue)\\b" }, { "name": "keyword.declaration.lyng", "match": "\\b(?:fun|fn|class|enum|interface|val|var|import|package|constructor|property|abstract|override|open|closed|extern|private|protected|static|get|set|object|init|by)\\b" }, { "name": "keyword.operator.word.lyng", "match": "\\bnot\\s+(?:in|is)\\b" }, { "name": "keyword.operator.word.lyng", "match": "\\b(?:and|or|not|in|is|as|as\\?)\\b" } ] },
+    "constants": { "patterns": [ { "name": "constant.language.lyng", "match": "(?:\\b(?:true|false|null|this(?:@[\\p{L}_][\\p{L}\\p{N}_]*)?)\\b|π)" } ] },
+    "types": { "patterns": [ { "name": "storage.type.lyng", "match": "\\b(?:Int|Real|String|Bool|Char|Regex)\\b" }, { "name": "entity.name.type.lyng", "match": "\\b[A-Z][A-Za-z0-9_]*\\b(?!\\s*\\()" } ] },
+    "operators": { "patterns": [ { "name": "keyword.operator.comparison.lyng", "match": "===|!==|==|!=|<=|>=|<|>" }, { "name": "keyword.operator.shuttle.lyng", "match": "<=>" }, { "name": "keyword.operator.arrow.lyng", "match": "=>|->|::" }, { "name": "keyword.operator.range.lyng", "match": "\\.\\.\\.|\\.\\.<|\\.\\." }, { "name": "keyword.operator.nullsafe.lyng", "match": "\\?\\.|\\?\\[|\\?\\(|\\?\\{|\\?:|\\?\\?" }, { "name": "keyword.operator.assignment.lyng", "match": "(?:\\+=|-=|\\*=|/=|%=|=)" }, { "name": "keyword.operator.logical.lyng", "match": "&&|\\|\\|" }, { "name": "keyword.operator.bitwise.lyng", "match": "<<|>>|&|\\||\\^|~" }, { "name": "keyword.operator.match.lyng", "match": "=~|!~" }, { "name": "keyword.operator.arithmetic.lyng", "match": "\\+\\+|--|[+\\-*/%]" }, { "name": "keyword.operator.other.lyng", "match": "[!?]" } ] },
+    "punctuation": { "patterns": [ { "name": "punctuation.separator.comma.lyng", "match": "," }, { "name": "punctuation.terminator.statement.lyng", "match": ";" }, { "name": "punctuation.section.block.begin.lyng", "match": "[(]{1}|[{]{1}|\\[" }, { "name": "punctuation.section.block.end.lyng", "match": "[)]{1}|[}]{1}|\\]" }, { "name": "punctuation.accessor.dot.lyng", "match": "\\." }, { "name": "punctuation.separator.colon.lyng", "match": ":" } ] }
+  }
+}

examples/tetris_console.lyng

@@ -0,0 +1,659 @@
+#!/usr/bin/env lyng
+
+/*
+ * Lyng Console Tetris (interactive sample)
+ *
+ * Controls:
+ *  - Left/Right arrows or A/D: move
+ *  - Up arrow or W: rotate
+ *  - Down arrow or S: soft drop
+ *  - Space: hard drop
+ *  - Q or Escape: quit
+ */
+
+import lyng.io.console
+
+val MIN_COLS = 56
+val MIN_ROWS = 24
+val PANEL_WIDTH = 24
+val BOARD_MARGIN_ROWS = 8
+val BOARD_MIN_W = 10
+val BOARD_MAX_W = 16
+val BOARD_MIN_H = 16
+val BOARD_MAX_H = 28
+val LEVEL_LINES_STEP = 10
+val DROP_FRAMES_BASE = 15
+val DROP_FRAMES_MIN = 3
+val FRAME_DELAY_MS = 35
+val RESIZE_WAIT_MS = 250
+val ROTATION_KICKS = [0, -1, 1, -2, 2]
+val ANSI_ESC = "\u001b["
+val ANSI_RESET = ANSI_ESC + "0m"
+val UNICODE_BLOCK = "██"
+val UNICODE_TOP_LEFT = "┌"
+val UNICODE_TOP_RIGHT = "┐"
+val UNICODE_BOTTOM_LEFT = "└"
+val UNICODE_BOTTOM_RIGHT = "┘"
+val UNICODE_HORIZONTAL = "──"
+val UNICODE_VERTICAL = "│"
+val UNICODE_DOT = "· "
+
+type Cell = List<Int>
+type Rotation = List<Cell>
+type Rotations = List<Rotation>
+type Row = List<Int>
+type Board = List<Row>
+
+class Piece(val name: String, val rotations: Rotations) {}
+class RotateResult(val ok: Bool, val rot: Int, val px: Int) {}
+class GameState(
+    pieceId0: Int,
+    nextId0: Int,
+    next2Id0: Int,
+    px0: Int,
+    py0: Int,
+) {
+    var pieceId = pieceId0
+    var nextId = nextId0
+    var next2Id = next2Id0
+    var rot = 0
+    var px = px0
+    var py = py0
+    var score = 0
+    var totalLines = 0
+    var level = 1
+    var running = true
+    var gameOver = false
+}
+class LoopFrame(val resized: Bool, val originRow: Int, val originCol: Int) {}
+
+fun clearAndHome() {
+    Console.clear()
+    Console.home()
+}
+
+fun repeatText(s: String, n: Int): String {
+    var out: String = ""
+    var i = 0
+    while (i < n) {
+        out += s
+        i = i + 1
+    }
+    out
+}
+
+fun maxInt(a: Int, b: Int): Int {
+    if (a > b) a else b
+}
+
+fun minInt(a: Int, b: Int): Int {
+    if (a < b) a else b
+}
+
+fun clampInt(v: Int, lo: Int, hi: Int): Int {
+    minInt(hi, maxInt(lo, v))
+}
+
+fun emptyRow(width: Int): Row {
+    val r: Row = []
+    var x = 0
+    while (x < width) {
+        r.add(0)
+        x = x + 1
+    }
+    r
+}
+
+fun createBoard(width: Int, height: Int): Board {
+    val b: Board = []
+    var y = 0
+    while (y < height) {
+        b.add(emptyRow(width))
+        y = y + 1
+    }
+    b
+}
+
+fun colorize(text: String, sgr: String, useColor: Bool): String {
+    if (!useColor) return text
+    ANSI_ESC + sgr + "m" + text + ANSI_RESET
+}
+
+fun blockText(pieceId: Int, useColor: Bool): String {
+    if (pieceId <= 0) return "  "
+    val sgr = when (pieceId) {
+        1 -> "36" // I
+        2 -> "33" // O
+        3 -> "35" // T
+        4 -> "32" // S
+        5 -> "31" // Z
+        6 -> "34" // J
+        7 -> "93" // L
+        else -> "37"
+    }
+    colorize(UNICODE_BLOCK, sgr, useColor)
+}
+
+fun emptyCellText(useColor: Bool): String {
+    colorize(UNICODE_DOT, "90", useColor)
+}
+
+fun canPlace(board: Board, boardW: Int, boardH: Int, pieceId: Int, rot: Int, px: Int, py: Int): Bool {
+    val piece: Piece = PIECES[pieceId - 1]
+    val cells = piece.rotations[rot]
+
+    for (cell in cells) {
+        val x = px + cell[0]
+        val y = py + cell[1]
+
+        if (x < 0 || x >= boardW) return false
+        if (y >= boardH) return false
+
+        if (y >= 0) {
+            val row = board[y]
+            if (row[x] != 0) return false
+        }
+    }
+    true
+}
+
+fun lockPiece(board: Board, pieceId: Int, rot: Int, px: Int, py: Int): Void {
+    val piece: Piece = PIECES[pieceId - 1]
+    val cells = piece.rotations[rot]
+
+    for (cell in cells) {
+        val x = px + cell[0]
+        val y = py + cell[1]
+
+        if (y >= 0) {
+            val row = board[y]
+            row[x] = pieceId
+        }
+    }
+}
+
+fun clearCompletedLines(board: Board, boardW: Int, boardH: Int): Int {
+    val b = board
+    var y = boardH - 1
+    var cleared = 0
+
+    while (y >= 0) {
+        val row = b[y]
+        var full = true
+        var x = 0
+        while (x < boardW) {
+            if (row[x] == 0) {
+                full = false
+                break
+            }
+            x = x + 1
+        }
+
+        if (full) {
+            b.removeAt(y)
+            b.insertAt(0, emptyRow(boardW))
+            cleared = cleared + 1
+        } else {
+            y = y - 1
+        }
+    }
+
+    cleared
+}
+
+fun activeCellId(pieceId: Int, rot: Int, px: Int, py: Int, x: Int, y: Int): Int {
+    val piece: Piece = PIECES[pieceId - 1]
+    val cells = piece.rotations[rot]
+
+    for (cell in cells) {
+        val ax = px + cell[0]
+        val ay = py + cell[1]
+        if (ax == x && ay == y) return pieceId
+    }
+
+    0
+}
+
+fun tryRotateCw(board: Board, boardW: Int, boardH: Int, pieceId: Int, rot: Int, px: Int, py: Int): RotateResult {
+    val piece: Piece = PIECES[pieceId - 1]
+    val rotations = piece.rotations.size
+    val nr = (rot + 1) % rotations
+    for (kx in ROTATION_KICKS) {
+        val nx = px + kx
+        if (canPlace(board, boardW, boardH, pieceId, nr, nx, py)) {
+            return RotateResult(true, nr, nx)
+        }
+    }
+    RotateResult(false, rot, px)
+}
+
+fun nextPreviewLines(pieceId: Int, useColor: Bool): List<String> {
+    val out: List<String> = []
+    if (pieceId <= 0) {
+        out.add("        ")
+        out.add("        ")
+        out.add("        ")
+        out.add("        ")
+        return out
+    }
+
+    val piece: Piece = PIECES[pieceId - 1]
+    val cells = piece.rotations[0]
+
+    var y = 0
+    while (y < 4) {
+        var line = ""
+        var x = 0
+        while (x < 4) {
+            var filled = false
+            for (cell in cells) {
+                if (cell[0] == x && cell[1] == y) {
+                    filled = true
+                    break
+                }
+            }
+            line += if (filled) blockText(pieceId, useColor) else "  "
+            x = x + 1
+        }
+        out.add(line)
+        y = y + 1
+    }
+    out
+}
+
+fun render(
+    state: GameState,
+    board: Board,
+    boardW: Int,
+    boardH: Int,
+    prevFrameLines: List<String>,
+    originRow: Int,
+    originCol: Int,
+    useColor: Bool,
+): List<String> {
+    val bottomBorder = UNICODE_BOTTOM_LEFT + repeatText(UNICODE_HORIZONTAL, boardW) + UNICODE_BOTTOM_RIGHT
+
+    val panel: List<String> = []
+    val nextPiece: Piece = PIECES[state.nextId - 1]
+    val next2Piece: Piece = PIECES[state.next2Id - 1]
+    val nextName = nextPiece.name
+    val next2Name = next2Piece.name
+    val preview = nextPreviewLines(state.nextId, useColor)
+
+    panel.add("Lyng Tetris")
+    panel.add("")
+    panel.add("Score: " + state.score)
+    panel.add("Lines: " + state.totalLines)
+    panel.add("Level: " + state.level)
+    panel.add("")
+    panel.add("Next: " + nextName)
+    panel.add("")
+    for (pl in preview) panel.add(pl)
+    panel.add("After: " + next2Name)
+    panel.add("")
+    panel.add("Keys:")
+    panel.add("A/D or arrows")
+    panel.add("W/Up: rotate")
+    panel.add("S/Down: drop")
+    panel.add("Space: hard drop")
+    panel.add("Q/Esc: quit")
+
+    val frameLines: List<String> = []
+
+    var y = 0
+    while (y < boardH) {
+        var line = UNICODE_VERTICAL
+
+        var x = 0
+        while (x < boardW) {
+            val a = activeCellId(state.pieceId, state.rot, state.px, state.py, x, y)
+            val row = board[y]
+            val b = row[x]
+            val id = if (a > 0) a else b
+            line += if (id > 0) blockText(id, useColor) else emptyCellText(useColor)
+            x = x + 1
+        }
+
+        line += UNICODE_VERTICAL
+
+        val p = y
+        if (p < panel.size) {
+            line += "   " + panel[p]
+        }
+
+        frameLines.add(line)
+        y = y + 1
+    }
+
+    frameLines.add(bottomBorder)
+
+    val prev = prevFrameLines
+    var i = 0
+    while (i < frameLines.size) {
+        val line = frameLines[i]
+        val old = if (i < prev.size) prev[i] else null
+        if (old != line) {
+            Console.moveTo(originRow + i, originCol)
+            Console.clearLine()
+            Console.write(line)
+        }
+        i = i + 1
+    }
+    frameLines
+}
+
+fun waitForMinimumSize(minCols: Int, minRows: Int): Object {
+    while (true) {
+        val g = Console.geometry()
+        val cols = g?.columns ?: 0
+        val rows = g?.rows ?: 0
+
+        if (cols >= minCols && rows >= minRows) return g
+
+        clearAndHome()
+        println("Lyng Tetris needs at least %sx%s terminal size."(minCols, minRows))
+        println("Current: %sx%s"(cols, rows))
+        println("Resize the console window to continue...")
+        delay(RESIZE_WAIT_MS)
+    }
+}
+
+fun scoreForLines(cleared: Int, level: Int): Int {
+    when (cleared) {
+        1 -> 100 * level
+        2 -> 300 * level
+        3 -> 500 * level
+        4 -> 800 * level
+        else -> 0
+    }
+}
+
+// Classic 7 tetrominoes, minimal rotations per piece.
+fun cell(x: Int, y: Int): Cell { [x, y] }
+fun rot(a: Cell, b: Cell, c: Cell, d: Cell): Rotation {
+    val r: Rotation = []
+    r.add(a)
+    r.add(b)
+    r.add(c)
+    r.add(d)
+    r
+}
+
+val PIECES: List<Piece> = []
+
+val iRots: Rotations = []
+iRots.add(rot(cell(0,1), cell(1,1), cell(2,1), cell(3,1)))
+iRots.add(rot(cell(2,0), cell(2,1), cell(2,2), cell(2,3)))
+PIECES.add(Piece("I", iRots))
+
+val oRots: Rotations = []
+oRots.add(rot(cell(1,0), cell(2,0), cell(1,1), cell(2,1)))
+PIECES.add(Piece("O", oRots))
+
+val tRots: Rotations = []
+tRots.add(rot(cell(1,0), cell(0,1), cell(1,1), cell(2,1)))
+tRots.add(rot(cell(1,0), cell(1,1), cell(2,1), cell(1,2)))
+tRots.add(rot(cell(0,1), cell(1,1), cell(2,1), cell(1,2)))
+tRots.add(rot(cell(1,0), cell(0,1), cell(1,1), cell(1,2)))
+PIECES.add(Piece("T", tRots))
+
+val sRots: Rotations = []
+sRots.add(rot(cell(1,0), cell(2,0), cell(0,1), cell(1,1)))
+sRots.add(rot(cell(1,0), cell(1,1), cell(2,1), cell(2,2)))
+PIECES.add(Piece("S", sRots))
+
+val zRots: Rotations = []
+zRots.add(rot(cell(0,0), cell(1,0), cell(1,1), cell(2,1)))
+zRots.add(rot(cell(2,0), cell(1,1), cell(2,1), cell(1,2)))
+PIECES.add(Piece("Z", zRots))
+
+val jRots: Rotations = []
+jRots.add(rot(cell(0,0), cell(0,1), cell(1,1), cell(2,1)))
+jRots.add(rot(cell(1,0), cell(2,0), cell(1,1), cell(1,2)))
+jRots.add(rot(cell(0,1), cell(1,1), cell(2,1), cell(2,2)))
+jRots.add(rot(cell(1,0), cell(1,1), cell(0,2), cell(1,2)))
+PIECES.add(Piece("J", jRots))
+
+val lRots: Rotations = []
+lRots.add(rot(cell(2,0), cell(0,1), cell(1,1), cell(2,1)))
+lRots.add(rot(cell(1,0), cell(1,1), cell(1,2), cell(2,2)))
+lRots.add(rot(cell(0,1), cell(1,1), cell(2,1), cell(0,2)))
+lRots.add(rot(cell(0,0), cell(1,0), cell(1,1), cell(1,2)))
+PIECES.add(Piece("L", lRots))
+
+if (!Console.isSupported()) {
+    println("Console API is not supported in this runtime.")
+    void
+} else if (!Console.isTty()) {
+    println("This sample needs an interactive terminal (TTY).")
+    void
+} else {
+    waitForMinimumSize(MIN_COLS, MIN_ROWS)
+
+    val g0 = Console.geometry()
+    val cols = g0?.columns ?: MIN_COLS
+    val rows = g0?.rows ?: MIN_ROWS
+
+    val boardW = clampInt((cols - PANEL_WIDTH) / 2, BOARD_MIN_W, BOARD_MAX_W)
+    val boardH = clampInt(rows - BOARD_MARGIN_ROWS, BOARD_MIN_H, BOARD_MAX_H)
+
+    val board: Board = createBoard(boardW, boardH)
+
+    fun nextPieceId() {
+        Random.next(1..7)
+    }
+
+    val state: GameState = GameState(
+        nextPieceId(),
+        nextPieceId(),
+        nextPieceId(),
+        (boardW / 2) - 2,
+        -1,
+    )
+    var prevFrameLines: List<String> = []
+
+    val gameMutex = Mutex()
+    var hasResizeEvent = false
+
+    val rawModeEnabled = Console.setRawMode(true)
+    if (!rawModeEnabled) {
+        println("Raw keyboard mode is not available in this terminal/runtime.")
+        println("Use jlyng in an interactive terminal with raw input support.")
+        void
+    } else {
+        val useColor = Console.ansiLevel() != "NONE"
+        Console.enterAltScreen()
+        Console.setCursorVisible(false)
+        clearAndHome()
+
+        fun applyKeyInput(s: GameState, key: String): Void {
+            if (key == "__CTRL_C__" || key == "q" || key == "Q" || key == "Escape") {
+                s.running = false
+            }
+            else if (key == "ArrowLeft" || key == "a" || key == "A") {
+                if (canPlace(board, boardW, boardH, s.pieceId, s.rot, s.px - 1, s.py)) s.px = s.px - 1
+            }
+            else if (key == "ArrowRight" || key == "d" || key == "D") {
+                if (canPlace(board, boardW, boardH, s.pieceId, s.rot, s.px + 1, s.py)) s.px = s.px + 1
+            }
+            else if (key == "ArrowUp" || key == "w" || key == "W") {
+                val rr: RotateResult = tryRotateCw(board, boardW, boardH, s.pieceId, s.rot, s.px, s.py)
+                if (rr.ok) {
+                    s.rot = rr.rot
+                    s.px = rr.px
+                }
+            }
+            else if (key == "ArrowDown" || key == "s" || key == "S") {
+                if (canPlace(board, boardW, boardH, s.pieceId, s.rot, s.px, s.py + 1)) {
+                    s.py = s.py + 1
+                    s.score = s.score + 1
+                }
+            }
+            else if (key == " ") {
+                while (canPlace(board, boardW, boardH, s.pieceId, s.rot, s.px, s.py + 1)) {
+                    s.py = s.py + 1
+                    s.score = s.score + 2
+                }
+            }
+        }
+
+        var inputRunning = true
+        launch {
+            while (inputRunning) {
+                try {
+                    for (ev in Console.events()) {
+                        if (!inputRunning) break
+                        if (ev is ConsoleKeyEvent) {
+                            val ke = ev as ConsoleKeyEvent
+                            if (ke.type == "keydown") {
+                                val key = ke.key
+                                val ctrl = ke.ctrl
+                                gameMutex.withLock {
+                                    val mapped = if (ctrl && (key == "c" || key == "C")) "__CTRL_C__" else key
+                                    applyKeyInput(state, mapped)
+                                }
+                            }
+                        } else if (ev is ConsoleResizeEvent) {
+                            gameMutex.withLock {
+                                hasResizeEvent = true
+                                prevFrameLines = []
+                            }
+                        }
+                    }
+                } catch (err: Exception) {
+                    // Keep game alive: transient console-event failures should not force quit.
+                    if (!inputRunning) break
+                    Console.setRawMode(true)
+                    delay(50)
+                }
+            }
+        }
+
+        fun pollLoopFrame(): LoopFrame? {
+            val g = Console.geometry()
+            val c = g?.columns ?: 0
+            val r = g?.rows ?: 0
+            if (c < MIN_COLS || r < MIN_ROWS) {
+                waitForMinimumSize(MIN_COLS, MIN_ROWS)
+                clearAndHome()
+                prevFrameLines = []
+                return null
+            }
+
+            var resized = false
+            gameMutex.withLock {
+                resized = hasResizeEvent
+                hasResizeEvent = false
+            }
+
+            val contentCols = boardW * 2 + 2 + 3 + PANEL_WIDTH
+            val contentRows = boardH + 1
+            val requiredCols = maxInt(MIN_COLS, contentCols)
+            val requiredRows = maxInt(MIN_ROWS, contentRows)
+            if (c < requiredCols || r < requiredRows) {
+                waitForMinimumSize(requiredCols, requiredRows)
+                clearAndHome()
+                prevFrameLines = []
+                return null
+            }
+
+            val originCol = maxInt(1, ((c - contentCols) / 2) + 1)
+            val originRow = maxInt(1, ((r - contentRows) / 2) + 1)
+            LoopFrame(resized, originRow, originCol)
+        }
+
+        fun advanceGravity(s: GameState, frame: Int): Int {
+            s.level = 1 + (s.totalLines / LEVEL_LINES_STEP)
+            val dropEvery = maxInt(DROP_FRAMES_MIN, DROP_FRAMES_BASE - s.level)
+
+            var nextFrame = frame + 1
+            if (nextFrame < dropEvery) return nextFrame
+            nextFrame = 0
+
+            if (canPlace(board, boardW, boardH, s.pieceId, s.rot, s.px, s.py + 1)) {
+                s.py = s.py + 1
+                return nextFrame
+            }
+
+            lockPiece(board, s.pieceId, s.rot, s.px, s.py)
+
+            val cleared = clearCompletedLines(board, boardW, boardH)
+            if (cleared > 0) {
+                s.totalLines = s.totalLines + cleared
+                s.score = s.score + scoreForLines(cleared, s.level)
+            }
+
+            s.pieceId = s.nextId
+            s.nextId = s.next2Id
+            s.next2Id = nextPieceId()
+            s.rot = 0
+            s.px = (boardW / 2) - 2
+            s.py = -1
+
+            if (!canPlace(board, boardW, boardH, s.pieceId, s.rot, s.px, s.py)) {
+                s.gameOver = true
+            }
+            nextFrame
+        }
+
+        try {
+            if (!canPlace(board, boardW, boardH, state.pieceId, state.rot, state.px, state.py)) {
+                state.gameOver = true
+            }
+
+            var frame = 0
+            var shouldStop = false
+            var prevOriginRow = -1
+            var prevOriginCol = -1
+            while (!shouldStop) {
+                val frameData = pollLoopFrame()
+                if (frameData == null) {
+                    frame = 0
+                    continue
+                }
+
+                gameMutex.withLock {
+                    if (!state.running || state.gameOver) {
+                        shouldStop = true
+                    } else {
+                        val movedOrigin = frameData.originRow != prevOriginRow || frameData.originCol != prevOriginCol
+                        if (frameData.resized || movedOrigin) {
+                            clearAndHome()
+                            prevFrameLines = []
+                        }
+                        prevOriginRow = frameData.originRow
+                        prevOriginCol = frameData.originCol
+                        frame = advanceGravity(state, frame)
+                        prevFrameLines = render(
+                            state,
+                            board,
+                            boardW,
+                            boardH,
+                            prevFrameLines,
+                            frameData.originRow,
+                            frameData.originCol,
+                            useColor
+                        )
+                    }
+                }
+                Console.flush()
+                delay(FRAME_DELAY_MS)
+            }
+        } finally {
+            inputRunning = false
+            Console.setRawMode(false)
+            Console.setCursorVisible(true)
+            Console.leaveAltScreen()
+            Console.flush()
+        }
+
+        if (state.gameOver) {
+            println("Game over.")
+        } else {
+            println("Bye.")
+        }
+        println("Score: %s"(state.score))
+        println("Lines: %s"(state.totalLines))
+        println("Level: %s"(state.level))
+    }
+}

gradle.properties

@@ -1,5 +1,5 @@
 #
-# Copyright 2025 Sergey S. Chernov real.sergeych@gmail.com
+# Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -16,7 +16,7 @@
 #
 
 #Gradle
-org.gradle.jvmargs=-Xmx2048M -Dfile.encoding=UTF-8 -Dkotlin.daemon.jvm.options\="-Xmx2048M"
+org.gradle.jvmargs=-Xmx4096M -Dfile.encoding=UTF-8 -Dkotlin.daemon.jvm.options\="-Xmx2048M"
 org.gradle.caching=true
 org.gradle.configuration-cache=true
 #Kotlin
@@ -29,3 +29,14 @@ android.nonTransitiveRClass=true
 
 # other
 kotlin.native.cacheKind.linuxX64=none
+
+# Workaround: Ensure Gradle uses a JDK with `jlink` available for AGP's JDK image transform.
+# On this environment, the system JDK 21 installation lacks `jlink`, causing
+# :lynglib:androidJdkImage to fail. Point Gradle to a JDK that includes `jlink`.
+# This affects only the JDK Gradle runs with; Kotlin/JVM target remains compatible.
+#org.gradle.java.home=/home/sergeych/.jdks/corretto-21.0.9
+android.experimental.lint.migrateToK2=false
+android.lint.useK2Uast=false
+kotlin.mpp.applyDefaultHierarchyTemplate=true
+
+org.gradle.parallel=true

gradle/libs.versions.toml

@@ -1,11 +1,13 @@
 [versions]
 agp = "8.5.2"
 clikt = "5.0.3"
-kotlin = "2.2.20"
+mordant = "3.0.2"
+kotlin = "2.3.0"
 android-minSdk = "24"
 android-compileSdk = "34"
 kotlinx-coroutines = "1.10.2"
-mp_bintools = "0.1.12"
+kotlinx-datetime = "0.6.1"
+mp_bintools = "0.3.2"
 firebaseCrashlyticsBuildtools = "3.0.3"
 okioVersion = "3.10.2"
 compiler = "3.2.0-alpha11"
@@ -13,13 +15,17 @@ compiler = "3.2.0-alpha11"
 [libraries]
 clikt = { module = "com.github.ajalt.clikt:clikt", version.ref = "clikt" }
 clikt-markdown = { module = "com.github.ajalt.clikt:clikt-markdown", version.ref = "clikt" }
+mordant-core = { module = "com.github.ajalt.mordant:mordant-core", version.ref = "mordant" }
+mordant-jvm-jna = { module = "com.github.ajalt.mordant:mordant-jvm-jna", version.ref = "mordant" }
 kotlin-test = { module = "org.jetbrains.kotlin:kotlin-test", version.ref = "kotlin" }
 kotlinx-coroutines-test = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-test", version.ref = "kotlinx-coroutines" }
 kotlinx-coroutines-core = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-core", version.ref = "kotlinx-coroutines" }
+kotlinx-datetime = { module = "org.jetbrains.kotlinx:kotlinx-datetime", version.ref = "kotlinx-datetime" }
 mp_bintools = { module = "net.sergeych:mp_bintools", version.ref = "mp_bintools" }
 firebase-crashlytics-buildtools = { group = "com.google.firebase", name = "firebase-crashlytics-buildtools", version.ref = "firebaseCrashlyticsBuildtools" }
 okio = { module = "com.squareup.okio:okio", version.ref = "okioVersion" }
 okio-fakefilesystem = { module = "com.squareup.okio:okio-fakefilesystem", version.ref = "okioVersion" }
+okio-nodefilesystem = { module = "com.squareup.okio:okio-nodefilesystem", version.ref = "okioVersion" }
 compiler = { group = "androidx.databinding", name = "compiler", version.ref = "compiler" }
 
 [plugins]

images/lyng-icons/lyng_file.svg

@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  - Copyright 2025 Sergey S. Chernov real.sergeych@gmail.com
+  -
+  - Licensed under the Apache License, Version 2.0 (the "License");
+  - you may not use this file except in compliance with the License.
+  - You may obtain a copy of the License at
+  -
+  -     http://www.apache.org/licenses/LICENSE-2.0
+  -
+  - Unless required by applicable law or agreed to in writing, software
+  - distributed under the License is distributed on an "AS IS" BASIS,
+  - WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  - See the License for the specific language governing permissions and
+  - limitations under the License.
+  -
+  -->
+
+<svg width="16" height="16" viewBox="0 0 16 16" xmlns="http://www.w3.org/2000/svg" aria-labelledby="title" role="img">
+  <title>Lyng File Icon (temporary λ)</title>
+  <defs>
+    <style>
+      .g { fill: none; stroke: currentColor; stroke-width: 1.6; stroke-linecap: round; stroke-linejoin: round; }
+    </style>
+  </defs>
+  <!-- Keep shapes crisp on small canvas; slight inset to avoid clipping -->
+  <g transform="translate(0.5,0.5)">
+    <!-- Stylized lambda fitted to 14x14 -->
+    <path class="g" d="M4.5 2.5 L7 9.5 C7.6 11.2 9.0 12.5 11.0 12.5 L14.5 12.5"/>
+    <path class="g" d="M7 9.5 L2.5 14.5"/>
+  </g>
+</svg>

images/lyng-icons/pluginIcon.svg

@@ -0,0 +1,33 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  - Copyright 2025 Sergey S. Chernov real.sergeych@gmail.com
+  -
+  - Licensed under the Apache License, Version 2.0 (the "License");
+  - you may not use this file except in compliance with the License.
+  - You may obtain a copy of the License at
+  -
+  -     http://www.apache.org/licenses/LICENSE-2.0
+  -
+  - Unless required by applicable law or agreed to in writing, software
+  - distributed under the License is distributed on an "AS IS" BASIS,
+  - WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  - See the License for the specific language governing permissions and
+  - limitations under the License.
+  -
+  -->
+
+<svg width="40" height="40" viewBox="0 0 40 40" xmlns="http://www.w3.org/2000/svg" aria-labelledby="title" role="img">
+  <title>Lyng Plugin Icon (temporary λ)</title>
+  <defs>
+    <!-- Monochrome, theme-friendly -->
+    <style>
+      .glyph { fill: none; stroke: currentColor; stroke-width: 3; stroke-linecap: round; stroke-linejoin: round; }
+    </style>
+  </defs>
+  <!-- Safe inset to avoid edge clipping in 40x40 canvas -->
+  <g transform="translate(2,2)">
+    <!-- Stylized lambda: rising stem + curved tail -->
+    <path class="glyph" d="M12 6 L18 22 C19.2 25.5 22.2 28 26 28 L32 28"/>
+    <path class="glyph" d="M18 22 L8 34"/>
+  </g>
+</svg>

lyng-idea/build.gradle.kts

@@ -0,0 +1,90 @@
+/*
+ * Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+plugins {
+    kotlin("jvm")
+    id("org.jetbrains.intellij") version "1.17.4"
+}
+
+group = "net.sergeych.lyng"
+version = "0.0.5-SNAPSHOT"
+
+kotlin {
+    jvmToolchain(17)
+}
+
+repositories {
+    mavenCentral()
+    // Use the same repositories as the rest of the project so plugin runtime deps resolve
+    maven("https://maven.universablockchain.com/")
+    maven("https://gitea.sergeych.net/api/packages/SergeychWorks/maven")
+    mavenLocal()
+}
+
+dependencies {
+    implementation(project(":lynglib"))
+    // Include lyngio so Quick Docs can reflectively load fs docs registrar (FsBuiltinDocs)
+    implementation(project(":lyngio"))
+    // Rich Markdown renderer for Quick Docs
+    implementation("com.vladsch.flexmark:flexmark-all:0.64.8")
+
+    // Tests for IntelliJ Platform fixtures rely on JUnit 3/4 API (junit.framework.TestCase)
+    // Add JUnit 4 which contains the JUnit 3 compatibility classes used by BasePlatformTestCase/UsefulTestCase
+    testImplementation("junit:junit:4.13.2")
+    testRuntimeOnly("org.junit.vintage:junit-vintage-engine:5.10.2")
+    testImplementation("org.opentest4j:opentest4j:1.3.0")
+}
+
+intellij {
+    type.set("IC")
+    // Build against a modern baseline. Install range is controlled by since/until below.
+    version.set("2024.1.6")
+    // We manage <idea-version> ourselves in plugin.xml to keep it open-ended (no upper cap)
+    updateSinceUntilBuild.set(false)
+    // Include only available bundled plugins for this IDE build
+    plugins.set(listOf(
+        "com.intellij.java",
+        // Provide Grazie API on compile classpath (bundled in 2024.3+, but add here for compilation)
+        "tanvd.grazi"
+        // Do not list com.intellij.spellchecker here: it is expected to be bundled with the IDE.
+        // Listing it causes Gradle to search for a separate plugin artifact and fail on IC 2024.3.
+    ))
+}
+
+tasks {
+    patchPluginXml {
+        // Keep version and other metadata patched by Gradle, but since/until are controlled in plugin.xml.
+        // (intellij.updateSinceUntilBuild=false prevents Gradle from injecting an until-build cap)
+    }
+
+    // Build an installable plugin zip and copy it to $PROJECT_ROOT/distributables
+    // Usage: ./gradlew :lyng-idea:buildInstallablePlugin
+    // It depends on buildPlugin and overwrites any existing file with the same name
+    register<Copy>("buildInstallablePlugin") {
+        dependsOn("buildPlugin")
+
+        // The Gradle IntelliJ Plugin produces: build/distributions/<project.name>-<version>.zip
+        val zipName = "${project.name}-${project.version}.zip"
+        val sourceZip = layout.buildDirectory.file("distributions/$zipName")
+
+        from(sourceZip)
+        into(rootProject.layout.projectDirectory.dir("distributables"))
+
+        // Overwrite if a file with the same name exists
+        duplicatesStrategy = DuplicatesStrategy.INCLUDE
+    }
+}

lyng-idea/src/main/kotlin/net/sergeych/lyng/idea/LyngFileType.kt

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2025 Sergey S. Chernov real.sergeych@gmail.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+package net.sergeych.lyng.idea
+
+import com.intellij.openapi.fileTypes.LanguageFileType
+import javax.swing.Icon
+
+object LyngFileType : LanguageFileType(LyngLanguage) {
+    override fun getName(): String = "Lyng"
+    override fun getDescription(): String = "Lyng language file"
+    override fun getDefaultExtension(): String = "lyng"
+    override fun getIcon(): Icon? = LyngIcons.FILE
+}

lyng-idea/src/main/kotlin/net/sergeych/lyng/idea/LyngFileTypeFactory.kt

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+package net.sergeych.lyng.idea
+
+import com.intellij.openapi.fileTypes.FileTypeConsumer
+import com.intellij.openapi.fileTypes.FileTypeFactory
+import com.intellij.openapi.fileTypes.WildcardFileNameMatcher
+
+/**
+ * Legacy way to register file type matchers, used here to robustly match *.lyng.d
+ * without conflicting with standard .d extensions from other plugins.
+ */
+@Suppress("DEPRECATION")
+class LyngFileTypeFactory : FileTypeFactory() {
+    override fun createFileTypes(consumer: FileTypeConsumer) {
+        // Register the multi-dot pattern explicitly
+        consumer.consume(LyngFileType, WildcardFileNameMatcher("*.lyng.d"))
+    }
+}

lyng-idea/src/main/kotlin/net/sergeych/lyng/idea/LyngIcons.kt

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2025 Sergey S. Chernov real.sergeych@gmail.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+package net.sergeych.lyng.idea
+
+import com.intellij.openapi.util.IconLoader
+import javax.swing.Icon
+
+object LyngIcons {
+    val FILE: Icon = IconLoader.getIcon("/icons/lyng_file.svg", LyngIcons::class.java)
+}

lyng-idea/src/main/kotlin/net/sergeych/lyng/idea/LyngLanguage.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2025 Sergey S. Chernov real.sergeych@gmail.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+package net.sergeych.lyng.idea
+
+import com.intellij.lang.Language
+
+object LyngLanguage : Language("Lyng")

lyng-idea/src/main/kotlin/net/sergeych/lyng/idea/actions/RunLyngScriptAction.kt

@@ -0,0 +1,109 @@
+/*
+ * Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package net.sergeych.lyng.idea.actions
+
+import com.intellij.execution.filters.TextConsoleBuilderFactory
+import com.intellij.execution.ui.ConsoleView
+import com.intellij.execution.ui.ConsoleViewContentType
+import com.intellij.openapi.actionSystem.AnAction
+import com.intellij.openapi.actionSystem.AnActionEvent
+import com.intellij.openapi.actionSystem.CommonDataKeys
+import com.intellij.openapi.project.Project
+import com.intellij.openapi.wm.ToolWindow
+import com.intellij.openapi.wm.ToolWindowAnchor
+import com.intellij.openapi.wm.ToolWindowId
+import com.intellij.openapi.wm.ToolWindowManager
+import com.intellij.psi.PsiFile
+import com.intellij.psi.PsiManager
+import com.intellij.ui.content.ContentFactory
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.launch
+import net.sergeych.lyng.idea.LyngIcons
+
+class RunLyngScriptAction : AnAction(LyngIcons.FILE) {
+    private val scope = CoroutineScope(Dispatchers.Default + SupervisorJob())
+
+    private fun getPsiFile(e: AnActionEvent): PsiFile? {
+        val project = e.project ?: return null
+        return e.getData(CommonDataKeys.PSI_FILE) ?: run {
+            val vf = e.getData(CommonDataKeys.VIRTUAL_FILE)
+            if (vf != null) PsiManager.getInstance(project).findFile(vf) else null
+        }
+    }
+
+    override fun update(e: AnActionEvent) {
+        val psiFile = getPsiFile(e)
+        val isLyng = psiFile?.name?.endsWith(".lyng") == true
+        e.presentation.isEnabledAndVisible = isLyng
+        if (isLyng) {
+            e.presentation.isEnabled = false
+            e.presentation.text = "Run '${psiFile.name}' (disabled)"
+            e.presentation.description = "Running scripts from the IDE is disabled; use the CLI."
+        } else {
+            e.presentation.text = "Run Lyng Script"
+        }
+    }
+
+    override fun actionPerformed(e: AnActionEvent) {
+        val project = e.project ?: return
+        val psiFile = getPsiFile(e) ?: return
+        val fileName = psiFile.name
+
+        val (console, toolWindow) = getConsoleAndToolWindow(project)
+        console.clear()
+
+        toolWindow.show {
+            scope.launch {
+                console.print("--- Run is disabled ---\n", ConsoleViewContentType.SYSTEM_OUTPUT)
+                console.print("Lyng now runs in bytecode-only mode; the IDE no longer evaluates scripts.\n", ConsoleViewContentType.NORMAL_OUTPUT)
+                console.print("Use the CLI to run scripts, e.g. `lyng run $fileName`.\n", ConsoleViewContentType.NORMAL_OUTPUT)
+            }
+        }
+    }
+
+    private fun getConsoleAndToolWindow(project: Project): Pair<ConsoleView, ToolWindow> {
+        val toolWindowManager = ToolWindowManager.getInstance(project)
+        var toolWindow = toolWindowManager.getToolWindow(ToolWindowId.RUN)
+        if (toolWindow == null) {
+            toolWindow = toolWindowManager.getToolWindow(ToolWindowId.MESSAGES_WINDOW)
+        }
+        if (toolWindow == null) {
+            toolWindow = toolWindowManager.getToolWindow("Lyng")
+        }
+        val actualToolWindow = toolWindow ?: run {
+            @Suppress("DEPRECATION")
+            toolWindowManager.registerToolWindow("Lyng", true, ToolWindowAnchor.BOTTOM)
+        }
+
+        val contentManager = actualToolWindow.contentManager
+        val existingContent = contentManager.findContent("Lyng Run")
+        if (existingContent != null) {
+            val console = existingContent.component as ConsoleView
+            contentManager.setSelectedContent(existingContent)
+            return console to actualToolWindow
+        }
+
+        val console = TextConsoleBuilderFactory.getInstance().createBuilder(project).console
+        val content = ContentFactory.getInstance().createContent(console.component, "Lyng Run", false)
+        contentManager.addContent(content)
+        contentManager.setSelectedContent(content)
+        return console to actualToolWindow
+    }
+}

lyng-idea/src/main/kotlin/net/sergeych/lyng/idea/annotators/LyngExternalAnnotator.kt

@@ -0,0 +1,194 @@
+/*
+ * Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package net.sergeych.lyng.idea.annotators
+
+import com.intellij.lang.annotation.AnnotationHolder
+import com.intellij.lang.annotation.ExternalAnnotator
+import com.intellij.lang.annotation.HighlightSeverity
+import com.intellij.openapi.editor.Document
+import com.intellij.openapi.progress.ProgressManager
+import com.intellij.openapi.util.Key
+import com.intellij.openapi.util.TextRange
+import com.intellij.psi.PsiFile
+import net.sergeych.lyng.highlight.HighlightKind
+import net.sergeych.lyng.highlight.offsetOf
+import net.sergeych.lyng.idea.highlight.LyngHighlighterColors
+import net.sergeych.lyng.idea.util.LyngAstManager
+import net.sergeych.lyng.tools.LyngDiagnosticSeverity
+import net.sergeych.lyng.tools.LyngLanguageTools
+import net.sergeych.lyng.tools.LyngSemanticKind
+
+/**
+ * ExternalAnnotator that runs Lyng MiniAst on the document text in background
+ * and applies semantic highlighting comparable with the web highlighter.
+ */
+class LyngExternalAnnotator : ExternalAnnotator<LyngExternalAnnotator.Input, LyngExternalAnnotator.Result>() {
+    data class Input(val text: String, val modStamp: Long, val previousSpans: List<Span>?, val file: PsiFile)
+
+    data class Span(val start: Int, val end: Int, val key: com.intellij.openapi.editor.colors.TextAttributesKey)
+    data class Diag(val start: Int, val end: Int, val message: String, val severity: HighlightSeverity)
+    data class Result(val modStamp: Long, val spans: List<Span>, val diagnostics: List<Diag> = emptyList())
+
+    override fun collectInformation(file: PsiFile): Input? {
+        val doc: Document = file.viewProvider.document ?: return null
+        val cached = file.getUserData(CACHE_KEY)
+        val combinedStamp = LyngAstManager.getCombinedStamp(file)
+
+        val prev = if (cached != null && cached.modStamp == combinedStamp) cached.spans else null
+        return Input(doc.text, combinedStamp, prev, file)
+    }
+
+    override fun doAnnotate(collectedInfo: Input?): Result? {
+        if (collectedInfo == null) return null
+        ProgressManager.checkCanceled()
+        val text = collectedInfo.text
+        val analysis = LyngAstManager.getAnalysis(collectedInfo.file)
+            ?: return Result(collectedInfo.modStamp, collectedInfo.previousSpans ?: emptyList())
+        val mini = analysis.mini
+
+        ProgressManager.checkCanceled()
+
+        val out = ArrayList<Span>(256)
+        val diags = ArrayList<Diag>()
+
+        fun putRange(start: Int, end: Int, key: com.intellij.openapi.editor.colors.TextAttributesKey) {
+            if (start in 0..end && end <= text.length && start < end) out += Span(start, end, key)
+        }
+
+        fun keyForKind(kind: LyngSemanticKind): com.intellij.openapi.editor.colors.TextAttributesKey? = when (kind) {
+            LyngSemanticKind.Function -> LyngHighlighterColors.FUNCTION
+            LyngSemanticKind.Class, LyngSemanticKind.Enum, LyngSemanticKind.TypeAlias -> LyngHighlighterColors.TYPE
+            LyngSemanticKind.Value -> LyngHighlighterColors.VALUE
+            LyngSemanticKind.Variable -> LyngHighlighterColors.VARIABLE
+            LyngSemanticKind.Parameter -> LyngHighlighterColors.PARAMETER
+            LyngSemanticKind.TypeRef -> LyngHighlighterColors.TYPE
+            LyngSemanticKind.EnumConstant -> LyngHighlighterColors.ENUM_CONSTANT
+        }
+
+        // Semantic highlights from shared tooling
+        LyngLanguageTools.semanticHighlights(analysis).forEach { span ->
+            keyForKind(span.kind)?.let { putRange(span.range.start, span.range.endExclusive, it) }
+        }
+
+        // Imports: each segment as namespace/path
+        mini?.imports?.forEach { imp ->
+            imp.segments.forEach { seg ->
+                if (seg.range.start.source === analysis.source && seg.range.end.source === analysis.source) {
+                    val start = analysis.source.offsetOf(seg.range.start)
+                    val end = analysis.source.offsetOf(seg.range.end)
+                    putRange(start, end, LyngHighlighterColors.NAMESPACE)
+                }
+            }
+        }
+
+        // Add annotation/label coloring using token highlighter
+        run {
+            analysis.lexicalHighlights.forEach { s ->
+                if (s.kind == HighlightKind.Label) {
+                    val start = s.range.start
+                    val end = s.range.endExclusive
+                    if (start in 0..end && end <= text.length && start < end) {
+                        val lexeme = try {
+                            text.substring(start, end)
+                        } catch (_: Throwable) {
+                            null
+                        }
+                        if (lexeme != null) {
+                            // Heuristic: if it starts with @ and follows a control keyword, it's likely a label
+                            // Otherwise if it starts with @ it's an annotation.
+                            // If it ends with @ it's a loop label.
+                            when {
+                                lexeme.endsWith("@") -> putRange(start, end, LyngHighlighterColors.LABEL)
+                                lexeme.startsWith("@") -> {
+                                    // Try to see if it's an exit label
+                                    val prevNonWs = prevNonWs(text, start)
+                                    val prevWord = if (prevNonWs >= 0) {
+                                        var wEnd = prevNonWs + 1
+                                        var wStart = prevNonWs
+                                        while (wStart > 0 && text[wStart - 1].isLetter()) wStart--
+                                        text.substring(wStart, wEnd)
+                                    } else null
+
+                                    if (prevWord in setOf("return", "break", "continue")) {
+                                        putRange(start, end, LyngHighlighterColors.LABEL)
+                                    } else {
+                                        putRange(start, end, LyngHighlighterColors.ANNOTATION)
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        analysis.diagnostics.forEach { d ->
+            val range = d.range ?: return@forEach
+            val severity = if (d.severity == LyngDiagnosticSeverity.Warning) HighlightSeverity.WARNING else HighlightSeverity.ERROR
+            diags += Diag(range.start, range.endExclusive, d.message, severity)
+        }
+
+        return Result(collectedInfo.modStamp, out, diags)
+    }
+
+
+    override fun apply(file: PsiFile, annotationResult: Result?, holder: AnnotationHolder) {
+        if (annotationResult == null) return
+        // Skip if cache is up-to-date
+        val combinedStamp = LyngAstManager.getCombinedStamp(file)
+        val cached = file.getUserData(CACHE_KEY)
+        val result = if (cached != null && cached.modStamp == combinedStamp) cached else annotationResult
+        file.putUserData(CACHE_KEY, result)
+
+        val doc = file.viewProvider.document
+
+        for (s in result.spans) {
+            holder.newSilentAnnotation(HighlightSeverity.INFORMATION)
+                .range(TextRange(s.start, s.end))
+                .textAttributes(s.key)
+                .create()
+        }
+
+        // Show errors and warnings
+        result.diagnostics.forEach { d ->
+            val start = d.start.coerceIn(0, (doc?.textLength ?: 0))
+            val end = d.end.coerceIn(start, (doc?.textLength ?: start))
+            if (end > start) {
+                holder.newAnnotation(d.severity, d.message)
+                    .range(TextRange(start, end))
+                    .create()
+            }
+        }
+    }
+
+    companion object {
+        private val CACHE_KEY: Key<Result> = Key.create("LYNG_SEMANTIC_CACHE")
+    }
+
+    private fun prevNonWs(text: String, idxExclusive: Int): Int {
+        var i = idxExclusive - 1
+        while (i >= 0) {
+            val ch = text[i]
+            if (ch != ' ' && ch != '\t' && ch != '\n' && ch != '\r') return i
+            i--
+        }
+        return -1
+    }
+
+    
+}