fix #31 type records for simple types and extern keyword for methods/functions

+collection functions (map, forEach, toList, toSet, isEmpty, etc,)

README.md

@@ -9,6 +9,10 @@ class Point(x,y) {
    fun dist() { sqrt(x*x + y*y) } 
 }
 Point(3,4).dist() //< 5
+
+fun swapEnds(first, args..., last, f) {
+    f( last, ...args, first)
+} 
 ```
 
 - extremely simple Kotlin integration on any platform
@@ -31,16 +35,42 @@ and it is multithreaded on platforms supporting it (automatically, no code chang
 
 ## Integration in Kotlin multiplatform
 
-### Add library
+### Add dependency to your project
 
-TBD
+```kotlin
+// update to current please:
+val lyngVersion = "0.6.1-SNAPSHOT"
+
+repositories {
+    // ...
+    maven("https://gitea.sergeych.net/api/packages/SergeychWorks/maven")
+}
+```
+
+And add dependency to the proper place in your project, it could look like:
+
+```kotlin
+comminMain by getting {
+    dependencies {
+        // ...
+        implementation("net.sergeych:lynglib:$lyngVersion")
+    }
+}
+```
+
+Now you can import lyng and use it:
 
 ### Execute script:
 
 ```kotlin
-assertEquals("hello, world", eval(""" 
-    "hello, " + "world" 
-    """).toString())
+import net.sergeyh.lyng.*
+
+// we need a coroutine to start, as Lyng
+// is a coroutine based language, async topdown
+runBlocking {
+    assert(5 == eval(""" 3*3 - 4 """).toInt())
+    eval(""" println("Hello, Lyng!") """)
+}
 ```
 
 ### Exchanging information
@@ -49,6 +79,8 @@ Script is executed over some `Context`. Create instance of the context,
 add your specific vars and functions to it, an call over it:
 
 ```kotlin
+import new.sergeych.lyng.* 
+
 // simple function
 val context = Context().apply {
     addFn("addArgs") {
@@ -83,22 +115,51 @@ Designed to add scripting to kotlin multiplatform application in easy and effici
 
 # Language 
 
-- dynamic 
-- async
-- multithreaded (coroutines could be dispatched using threads on appropriate platforms, automatically)
+- Javascript, WasmJS, native, JVM, android - batteries included.
+- dynamic types in most elegant and concise way
+- async, 100% coroutines, supports multiple cores where platofrm supports thread
+- good for functional an object-oriented style
 
-## By-stage
+# Language Roadmap
 
-Here are plans to develop it:
+## v1.0.0
 
-### First stage
+Planned autumn 2025. Complete dynamic language with sufficient standard library:
 
-Interpreted, precompiled into threaded code, actually. Dynamic types.
+Ready features:
 
-### Second stage
+- [x] Language platform and independent command-line launcher
+- [x] Integral types and user classes, variables and constants, functions
+- [x] lambdas and closures, coroutines for all callables
+- [x] while-else, do-while-else, for-else loops with break-continue returning values and labels support
+- [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] multiplatform maven publication
+- [x] documentation for the current state
 
-Will add:
+Under way: 
 
-- optimizations
-- p-code serialization
-- static typing
+- [ ] maps, sets and sequences (flows?)
+- [ ] regular exceptions
+- [ ] modules
+- [ ] string interpolation and more string tools
+- [ ] multiple inheritance for user classes
+- [ ] launch, deferred, coroutineScope, mutex, etc.
+- [ ] site with integrated interpreter to give a try
+- [ ] kotlin part public API good docs, integration focused
+- [ ] better stack reporting
+
+## v1.1+
+
+Planned features.
+
+- [ ] type specifications
+- [ ] source docs and maybe lyng.md to a standard
+- [ ] moacro-style kotlin integration or something else to simplify it
+
+Further
+
+- [ ] client with GUI support based on compose multiplatform somehow
+- [ ] notebook - style workbooks with graphs, formulaes, etc.
+- [ ] language server or compose-based lyng-aware editor

bin/lyng_test

@@ -0,0 +1,3 @@
+#!/usr/bin/env lyng
+
+println("Hello from lyng!")

docs/Collection.md

@@ -0,0 +1,13 @@
+# Collection
+
+Is a [Iterable] with known `size`, a finite [Iterable]:
+
+    class Collection : Iterable {
+        val size
+    }
+
+See [List], [Set] and [Iterable]
+
+[Iterable]: Iterable.md
+[List]: List.md
+[Set]: Set.md

docs/Iterable.md

@@ -1,13 +1,17 @@
 # Iterable interface
 
-The inteface which requires iterator to be implemented:
+Iterable is a class that provides function that creates _the iterator_:
 
-    fun iterator(): Iterator
+    class Iterable {
+        abstract fun iterator()
+    }
+
+Note that each call of `iterator()` must provide an independent iterator.
 
 Iterator itself is a simple interface that should provide only to method:
 
-    interface Iterable {
-        fun hasNext(): Bool
+    class Iterator {
+        abstract fun hasNext(): Bool
         fun next(): Obj
     }
 
@@ -15,19 +19,26 @@ Just remember at this stage typed declarations are not yet supported.
 
 Having `Iterable` in base classes allows to use it in for loop. Also, each `Iterable` has some utility functions available:
 
+## Instance methods
+
+    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
+    
+
 ## Abstract methods
 
     fun iterator(): Iterator
 
-## Instance methods
-
-### toList()
-
 Creates a list by iterating to the end. So, the Iterator should be finite to be used with it.
 
 ## Included in interfaces:
 
-- Collection, Array, [List]
+- [Collection], Array, [List]
 
 ## Implemented in classes:
 

docs/List.md

@@ -20,11 +20,11 @@ indexing is zero-based, as in C/C++/Java/Kotlin, etc.
     list[1]
     >>> 20
 
-Using negative indexes has a special meaning: _offset from the end of the list_:
+There is a shortcut for the last:
 
     val list = [10, 20, 30]
-    list[-1]
-    >>> 30
+    [list.last, list.lastIndex]
+    >>> [30, 2]
 
 __Important__ negative indexes works wherever indexes are used, e.g. in insertion and removal methods too.
 
@@ -38,7 +38,8 @@ You can concatenate lists or iterable objects:
 
 ## Appending
 
-To append to lists, use `+=` with elements, lists and any [Iterable] instances, but beware it will concatenate [Iterable] objects instead of appending them. To append [Iterable] instance itself, use `list.add`:
+To append to lists, use `+=` with elements, lists and any [Iterable] instances, but beware it will
+concatenate [Iterable] objects instead of appending them. To append [Iterable] instance itself, use `list.add`:
 
     var list = [1, 2]
     val other = [3, 4]
@@ -57,7 +58,28 @@ To append to lists, use `+=` with elements, lists and any [Iterable] instances,
 
     >>> void
 
+## Removing elements
 
+List is mutable, so it is possible to remove its contents. To remove a single element
+by index use:
+
+    assertEquals( [1,2,3].removeAt(1), [1,3] )
+    assertEquals( [1,2,3].removeAt(0), [2,3] )
+    assertEquals( [1,2,3].removeLast(), [1,2] )
+    >>> void
+
+There is a way to remove a range (see [Range] for more on ranges):
+
+    assertEquals( [1, 4], [1,2,3,4].removeRange(1..2))
+    assertEquals( [1, 4], [1,2,3,4].removeRange(1..<3))
+    >>> void
+
+Open end ranges remove head and tail elements:
+
+    assertEquals( [3, 4, 5], [1,2,3,4,5].removeRange(..1))
+    assertEquals( [3, 4, 5], [1,2,3,4,5].removeRange(..<2))
+    assertEquals( [1, 2], [1,2,3,4,5].removeRange( (2..) ))
+    >>> void
 
 ## Comparisons
 
@@ -72,19 +94,44 @@ To append to lists, use `+=` with elements, lists and any [Iterable] instances,
 
 ## Members
 
-| name                              | meaning                             | type     |
-|-----------------------------------|-------------------------------------|----------|
-| `size`                            | current size                        | Int      |
-| `add(elements...)`                | add one or more elements to the end | Any      |
-| `addAt(index,elements...)`        | insert elements at position         | Int, Any |
-| `removeAt(index)`                 | remove element at position          | Int      |
-| `removeRangeInclusive(start,end)` | remove range, inclusive (1)         | Int, Int |
-|                                   |                                     |          |
+| name                          | meaning                               | type        |
+|-------------------------------|---------------------------------------|-------------|
+| `size`                        | current size                          | Int         |
+| `add(elements...)`            | add one or more elements to the end   | Any         |
+| `insertAt(index,elements...)` | insert elements at position           | Int, Any    |
+| `removeAt(index)`             | remove element at position            | Int         |
+| `remove(from,toNonInclusive)` | remove range from (incl) to (nonincl) | Int, Int    |
+| `remove(Range)`               | remove range                          | Range       |
+| `removeLast()`                | remove last element                   |             |
+| `removeLast(n)`               | remove n last elements                | Int         |
+| `contains(element)`           | check the element is in the list (1)  |             |
+| `[index]`                     | get or set element at index           | Int         |
+| `[Range]`                     | get slice of the array (copy)         | Range       |
+| `+=`                          | append element(s)                     | List or Obj |
 
 (1)
-: end-inclisiveness allows to use negative indexes to, for exampe, remove several last elements, like `list.removeRangeInclusive(-2, -1)` will remove two last elements.
+: optimized implementation that override `Array` one
+
+(2)
+: `+=` append either a single element, or all elements if the List or other Iterable
+instance is appended. If you want to append an Iterable object itself, use `add` instead.
+
+It inherits from [Iterable] too.
+
+## Member inherited from Array
+
+| name             | meaning                        | type  |
+|------------------|--------------------------------|-------|
+| `last`           | last element (throws if empty) |       |
+| `lastOrNull`     | last element or null           |       |
+| `lastIndex`      |                                | Int   |
+| `indices`        | range of indexes               | Range |
+| `contains(item)` | test that item is in the list  |       |
+
+(1)
+: end-inclisiveness allows to use negative indexes to, for exampe, remove several last elements, like
+`list.removeRangeInclusive(-2, -1)` will remove two last elements.
 
 
-# Notes
-
-Could be rewritten using array as a class but List as the interface
+[Range]: Range.md
+[Iterable]: Iterable.md

docs/Map.md

@@ -0,0 +1,109 @@
+# 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].
+
+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)
+    >>> void
+
+Map keys could be any objects (hashable, e.g. with reasonable hashCode, most of standard types are). You can access elements with indexing operator:
+
+    val map = Map( ["foo", 1], ["bar", "buzz"], [42, "answer"] )
+    assert( map["bar"] == "buzz")
+    assert( map[42] == "answer" )
+    assertThrows { map["nonexistent"] }
+    assert( map.getOrNull(101) == null )
+    assert( map.getOrPut(911) { "nine-eleven" } == "nine-eleven" )
+    // now 91 entry is set:
+    assert( map[911] == "nine-eleven" )
+    map["foo"] = -1
+    assert( map["foo"] == -1)
+    >>> void
+
+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.
+
+    val map = Map( ["foo", 1], ["bar", "buzz"], [42, "answer"] )
+    assertEquals( 1, map.remove("foo") )
+    assert( map.getOrNull("foo") == null)
+    assert( map.size == 2 )
+    map.clear()
+    assert( map.size == 0 )
+    >>> void
+
+Map implements [contains] method that checks _the presence of the key_ in the map:
+
+    val map = Map( ["foo", 1], ["bar", "buzz"], [42, "answer"] )
+    assert( "foo" in map )
+    assert( "answer" !in map )
+    >>> void
+
+To iterate maps it is convenient to use `keys` method that returns [Set] of keys (keys are unique:
+
+    val map = Map( ["foo", 1], ["bar", "buzz"], [42, "answer"] )
+    for( k in map.keys ) println(map[k])
+    >>> 1
+    >>> buzz
+    >>> answer
+    >>> void
+
+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))
+    }
+    void
+    >>> map[foo] = 1
+    >>> map[bar] = buzz
+    >>> map[42] = answer
+    >>> void
+
+There is a shortcut to use `MapEntry` to create maps: operator `=>` which creates `MapEntry`:
+
+    val entry = "answer" => 42
+    assert( entry is MapEntry )
+    >>> void
+
+And you can use it to construct maps:
+
+    val map = Map( "foo" => 1, "bar" => 22)
+    assertEquals(1, map["foo"])
+    assertEquals(22, map["bar"])
+    >>> void
+
+Or use `.toMap` on anything that implements [Iterable] and which elements implements [Array] with 2 elements size, for example, `MapEntry`:
+
+    val map = ["foo" => 1, "bar" => 22].toMap()
+    assert( map is Map )
+    assertEquals(1, map["foo"])
+    assertEquals(22, map["bar"])
+    >>> void
+
+
+It is possible also to get values as [List] (values are not unique):
+
+    val map = Map( ["foo", 1], ["bar", "buzz"], [42, "answer"] )
+    assertEquals(map.values, [1, "buzz", "answer"] )
+    >>> void
+
+Map could be tested to be equal: when all it key-value pairs are equal, the map
+is equal.
+
+    val m1 = Map(["foo", 1])
+    val m2 = Map(["foo", 1])
+    val m3 = Map(["foo", 2])
+    assert( m1 == m2 )
+    // but the references are different:
+    assert( m1 !== m2 )
+    // different maps:
+    assert( m1 != m3 )
+    >>> void
+
+[Collection](Collection.md)

docs/Set.md

@@ -0,0 +1,94 @@
+# List 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.
+
+    val set = Set(1,2,3, "foo")
+    assert( 1 in set )
+    assert( "foo" in set)
+    assert( "bar" !in set)
+    >>> void
+
+## Set is collection and therefore [Iterable]:
+
+    assert( Set(1,2) is Set)
+    assert( Set(1,2) is Iterable)
+    assert( Set(1,2) is Collection)
+    >>> void
+
+So it supports all methods from [Iterable]; set is not, though, an [Array] and has
+no indexing. Use [set.toList] as needed.
+
+## Set operations
+
+    // Union
+    assertEquals( Set(1,2,3,4), Set(3, 1) + Set(2, 4))
+
+    // 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) )
+
+    // To find collection elements not present in another collection, use the 
+    // subtract() or `-`:
+    assertEquals( Set( 1, 2), Set(1, 2, 4, 3) - Set(3, 4))
+
+    >>> void
+
+## Adding elements
+
+    var s = Set()
+    s += 1
+    assertEquals( Set(1), s)
+    
+    s += [3, 3, 4]
+    assertEquals( Set(3, 4, 1), s)
+    >>> void
+
+## Removing elements
+
+List is mutable, so it is possible to remove its contents. To remove a single element
+by index use:
+
+    var s = Set(1,2,3)
+    s.remove(2)
+    assertEquals( s, Set(1,3) )
+
+    s = Set(1,2,3)
+    s.remove(2,1)
+    assertEquals( s, Set(3) )
+    >>> void
+
+Note that `remove` returns true if at least one element was actually removed and false
+if the set has not been changed.
+
+## Comparisons and inclusion
+
+Sets are only equal when contains exactly same elements, order, as was said, is not significant:
+
+    assert( Set(1, 2) == Set(2, 1) )
+    assert( Set(1, 2, 2) == Set(2, 1) )
+    assert( Set(1, 3) != Set(2, 1) )
+    assert( 1 in Set(5,1))
+    assert( 10 !in Set(5,1))
+    >>> void
+
+## Members
+
+| name                | meaning                              | type  |
+|---------------------|--------------------------------------|-------|
+| `size`              | current size                         | Int   |
+| `+=`                | add one or more elements             | Any   |
+| `+`, `union`         | union sets                           | Any   |
+| `-`, `subtract`     | subtract sets                        | Any   |
+| `*`, `intersect`    | subtract sets                        | Any   |
+| `remove(items...)`  | remove one or more items             | Range |
+| `contains(element)` | check the element is in the list (1) |       |
+
+(1)
+: optimized implementation that override `Iterable` one
+
+Also, it inherits methods from [Iterable].
+
+
+[Range]: Range.md

docs/advanced_topics.md

@@ -86,4 +86,28 @@ Lambda functions remember their scopes, so it will work the same as previous:
     val c = createLambda()
     println(c)
     >> 1
-    >> void
+    >> void
+
+# Elements of functional programming
+
+With ellipsis and splats you can create partial functions, manipulate
+arguments list in almost arbitrary ways. For example:
+
+    // Swap first and last arguments for call
+
+    fun swap_args(first, others..., last, f) { 
+        f(last, ...others, first) 
+    }
+
+    fun glue(args...) {
+        var result = ""
+        for( a in args ) result += a
+    }
+
+    assertEquals( 
+        "4231", 
+        swap_args( 1, 2, 3, 4, glue)
+    )
+    >>> void
+
+,

docs/exceptions_handling.md

@@ -131,7 +131,7 @@ _this functionality is not yet released_
 | class                      | notes                                                 |
 |----------------------------|-------------------------------------------------------|
 | Exception                  | root of al throwable objects                          |
-| NullPointerException       |                                                       |
+| NullReferenceException       |                                                       |
 | AssertionFailedException   |                                                       | 
 | ClassCastException         |                                                       |
 | IndexOutOfBoundsException  |                                                       |

docs/tutorial.md

@@ -14,7 +14,7 @@ __Other documents to read__ maybe after this one:
 - [Advanced topics](advanced_topics.md), [declaring arguments](declaring_arguments.md)
 - [OOP notes](OOP.md), [exception handling](exceptions_handling.md)
 - [math in Lyng](math.md)
-- Some class references: [List], [Real], [Range], [Iterable], [Iterator]
+- Some class references: [List], [Set], [Map], [Real], [Range], [Iterable], [Iterator]
 - Some samples: [combinatorics](samples/combinatorics.lyng.md), national vars and loops: [сумма ряда](samples/сумма_ряда.lyng.md). More at [samples folder](samples)
 
 # Expressions
@@ -118,6 +118,109 @@ These operators return rvalue, unmodifiable.
 
 ## Assignment return r-value!
 
+Naturally, assignment returns its value:
+
+    var x
+    x = 11
+    >>> 11
+
+rvalue means you cant assign the result if the assignment
+
+    var x
+    assertThrows { (x = 11) = 5 }
+    void
+    >>> void
+
+This also prevents chain assignments so use parentheses:
+
+    var x
+    var y
+    x = (y = 1)
+    >>> 1
+
+## Nullability
+
+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() }
+    
+    assert( ref?.field == null )
+    assert( ref?.method() == null )
+    assert( ref?.array?[1] == null )
+    assert( ref?[1] == null )
+    assert( ref?() == null )
+    >>> void
+
+There is also "elvis operator", null-coalesce infix operator '?:' that returns rvalue if lvalue is `null`:
+
+    null ?: "nothing"
+    >>> "nothing"
+
+## Utility functions
+
+The following functions simplify nullable values processing and
+allow to improve code look and readability. There are borrowed from Kotlin:
+
+### let 
+
+`value.let {}` passes to the block value as the single parameter (by default it is assigned to `it`) and return block's returned value. It is useful dealing with null or to
+get a snapshot of some externally varying value, or with `?.` to process nullable value in a safe manner:
+
+    // this state is changed from parallel processes
+    class GlobalState(nullableParam)
+    
+    val state = GlobalState(null)
+
+    fun sample() {
+        state.nullableParam?.let { "it's not null: "+it} ?: "it's null"
+    }
+    assertEquals(sample(), "it's null")
+    state.nullableParam = 5
+    assertEquals(sample(), "it's not null: 5")
+    >>> void
+
+This is the same as:
+
+    fun sample() {
+        val it = state.nullableParam
+        if( it != null )  "it's not null: "+it else "it's null"
+    }
+
+The important is that nullableParam got a local copy that can't be changed from any
+parallel thread/coroutine. Remember: Lyng _is __not__ a single-threaded language_.
+
+## Also
+
+Much like let, but it does not alter returned value:
+
+    assert( "test".also { println( it + "!") } == "test" )
+    >>> test!
+    >>> 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++ }
+    assertEquals(p.x, 2)
+    >>> void
+
+## apply
+
+It works much like `also`, but is executed in the context of the source object:
+
+    class Point(x,y)
+    // see the difference: apply changes this to newly created Point:
+    val p = Point(1,2).apply { x++; y++ }
+    assertEquals(p, Point(2,3))
+    >>> void
+
 ## Math
 
 It is rather simple, like everywhere else:
@@ -469,64 +572,97 @@ To add elements to the list:
     assert( x == [1, 2, 3, "the", "end"])
     >>> void
 
-Self-modifying concatenation by `+=` also works:
+Self-modifying concatenation by `+=` also works (also with single elements):
 
     val x = [1, 2]
     x += [3, 4]
-    assert( x == [1, 2, 3, 4])
+    x += 5
+    assert( x == [1, 2, 3, 4, 5])
     >>> void
 
-You can insert elements at any position using `addAt`:
+You can insert elements at any position using `insertAt`:
 
     val x = [1,2,3]
-    x.addAt(1, "foo", "bar")
+    x.insertAt(1, "foo", "bar")
     assert( x == [1, "foo", "bar", 2, 3])
     >>> void
 
 Using splat arguments can simplify inserting list in list:
 
     val x = [1, 2, 3]
-    x.addAt( 1, ...[0,100,0])
+    x.insertAt( 1, ...[0,100,0])
     x
     >>> [1, 0, 100, 0, 2, 3]
 
-Using negative indexes can insert elements as offset from the end, for example:
-
-    val x = [1,2,3]
-    x.addAt(-1, 10)
-    x
-    >>> [1, 2, 10, 3]
 
 Note that to add to the end you still need to use `add` or positive index of the after-last element:
 
     val x = [1,2,3]
-    x.addAt(3, 10)
+    x.insertAt(3, 10)
     x
     >>> [1, 2, 3, 10]
 
+but it is much simpler, and we recommend to use '+='
+
+    val x = [1,2,3]
+    x += 10
+    >>> [1, 2, 3, 10]
+
 ## Removing list items
 
     val x = [1, 2, 3, 4, 5]
     x.removeAt(2)
     assert( x == [1, 2, 4, 5])
     // or remove range (start inclusive, end exclusive):
-    x.removeRangeInclusive(1,2)    
+    x.removeRange(1..2)    
     assert( x == [1, 5])
     >>> void
 
-Again, you can use negative indexes. For example, removing last elements like:
+There is a shortcut to remove the last elements:
 
     val x = [1, 2, 3, 4, 5]
 
     // remove last:
-    x.removeAt(-1)
+    x.removeLast()
     assert( x == [1, 2, 3, 4])
     
     // remove 2 last:
-    x.removeRangeInclusive(-2,-1)
-    assert( x == [1, 2])
+    x.removeLast(2)
+    assertEquals( [1, 2], x)
     >>> void
 
+You can get ranges to extract a portion from a list:
+
+    val list = [1, 2, 3, 4, 5]
+    assertEquals( [1,2,3], list[..2])
+    assertEquals( [1,2,], list[..<2])
+    assertEquals( [4,5], list[3..])
+    assertEquals( [2,3], list[1..2])
+    assertEquals( [2,3], list[1..<3])
+    >>> void
+
+# Sets
+
+Set are unordered collection of unique elements, see [Set]. Sets are [Iterable] but have no indexing access.
+
+    assertEquals( Set(3, 2, 1), Set( 1, 2, 3))
+    assert( 5 !in Set(1, 2, 6) )
+    >>> void
+
+Please see [Set] for detailed description.
+
+# Maps
+
+Maps are unordered collection of key-value pairs, where keys are unique. See [Map] for details. Map also
+are [Iterable]:
+
+    val m = Map( "foo" => 77, "bar" => "buzz" )
+    assertEquals( m["foo"], 77 )
+    >>> void
+
+Please see [Map] reference for detailed description on using Maps.
+
+
 # Flow control operators
 
 ## if-then-else
@@ -1006,31 +1142,79 @@ Are the same as in string literals with little difference:
 
 ## String details
 
-Strings are much like Kotlin ones:
+Strings are arrays of Unicode characters. It can be indexed, and indexing will
+return a valid Unicode character at position. No utf hassle:
 
-    "Hello".length
+    "Парашют"[5]
+    >>> 'ю'
+
+Its length is, of course, in characters:
+
+    "разум".length
     >>> 5
+
 And supports growing set of kotlin-borrowed operations, see below, for example:
 
     assertEquals("Hell", "Hello".dropLast(1))
     >>> void
 
+To format a string use sprintf-style modifiers like:
+
+    val a = "hello"
+    val b = 11
+    assertEquals( "hello:11", "%s:%d"(a, b) )
+    assertEquals( " hello:    11", "%6s:%6d"(a, b) )
+    assertEquals( "hello :11    ", "%-6s:%-6d"(a, b) )
+    >>> void
+
+List of format specifiers closely resembles C sprintf() one. See [format specifiers](https://github.com/sergeych/mp_stools?tab=readme-ov-file#sprintf-syntax-summary), this is doe using [mp_stools kotlin multiplatform library](https://github.com/sergeych/mp_stools). Currently supported Lyng types are `String`, `Int`, `Real`, `Bool`, the rest are displayed using their `toString()` representation.
+
+This list will be extended.
+
+To get the substring use:
+
+    assertEquals("pult", "catapult".takeLast(4))
+    assertEquals("cat", "catapult".take(3))
+    assertEquals("cat", "catapult".dropLast(5))
+    assertEquals("pult", "catapult".drop(4))
+    >>> void
+
+And to get a portion you can slice it with range as the index:
+
+    assertEquals( "tap", "catapult"[ 2 .. 4 ])
+    assertEquals( "tap", "catapult"[ 2 ..< 5 ])
+    >>> void
+
+Open-ended ranges could be used to get start and end too:
+
+    assertEquals( "cat", "catapult"[ ..< 3 ])
+    assertEquals( "cat", "catapult"[ .. 2 ])
+    assertEquals( "pult", "catapult"[ 4.. ])
+    >>> void
+
 ### String operations
 
 Concatenation is a `+`: `"hello " + name` works as expected. No confusion.
 
 Typical set of String functions includes:
 
-| fun/prop         | description / notes                                        |
-|------------------|------------------------------------------------------------|
-| lower()          | change case to unicode upper                               |
-| upper()          | change case to unicode lower                               |
+| fun/prop           | description / notes                                        |
+|--------------------|------------------------------------------------------------|
+| lower()            | change case to unicode upper                               |
+| upper()            | change case to unicode lower                               |
 | startsWith(prefix) | true if starts 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] |
+| 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                                         |
+| s1 + s2            | concatenation                                              |
+| s1 += s2           | self-modifying concatenation                               |
+
 
 
 
@@ -1066,5 +1250,7 @@ See [math functions](math.md). Other general purpose functions are:
 [Iterator]: Iterator.md
 [Real]: Real.md
 [Range]: Range.md
-
-
+[String]: String.md
+[string formatting]: https://github.com/sergeych/mp_stools?tab=readme-ov-file#sprintf-syntax-summary
+[Set]: Set.md
+[Map]: Map.md

happy.py

@@ -1,11 +0,0 @@
-count = 0
-for n1 in range(10):
-    for n2 in range(10):
-        for n3 in range(10):
-            for n4 in range(10):
-                for n5 in range(10):
-                    for n6 in range(10):
-                        if n1 + n2 + n3 == n4 + n5 + n6:
-                            count += 1
-
-print(count)

library/src/commonMain/kotlin/net/sergeych/lyng/ObjClass.kt

@@ -1,173 +0,0 @@
-package net.sergeych.lyng
-
-val ObjClassType by lazy { ObjClass("Class") }
-
-open class ObjClass(
-    val className: String,
-    vararg val parents: ObjClass,
-) : Obj() {
-
-    var instanceConstructor: Statement? = null
-
-    val allParentsSet: Set<ObjClass> = parents.flatMap {
-        listOf(it) + it.allParentsSet
-    }.toSet()
-
-    override val objClass: ObjClass by lazy { ObjClassType }
-
-    // members: fields most often
-    private val members = mutableMapOf<String, ObjRecord>()
-
-    override fun toString(): String = className
-
-    override suspend fun compareTo(context: Context, other: Obj): Int = if (other === this) 0 else -1
-
-    override suspend fun callOn(context: Context): Obj {
-        val instance = ObjInstance(this)
-        instance.instanceContext = context.copy(newThisObj = instance,args = context.args)
-        if (instanceConstructor != null) {
-            instanceConstructor!!.execute(instance.instanceContext)
-        }
-        return instance
-    }
-
-    fun defaultInstance(): Obj = object : Obj() {
-        override val objClass: ObjClass = this@ObjClass
-    }
-
-    fun createField(
-        name: String,
-        initialValue: Obj,
-        isMutable: Boolean = false,
-        visibility: Visibility = Visibility.Public,
-        pos: Pos = Pos.builtIn
-    ) {
-        val existing = members[name] ?: allParentsSet.firstNotNullOfOrNull { it.members[name] }
-        if( existing?.isMutable == false)
-            throw ScriptError(pos, "$name is already defined in $objClass or one of its supertypes")
-        members[name] = ObjRecord(initialValue, isMutable, visibility)
-    }
-
-    fun addFn(name: String, isOpen: Boolean = false, code: suspend Context.() -> Obj) {
-        createField(name, statement { code() }, isOpen)
-    }
-
-    fun addConst(name: String, value: Obj) = createField(name, value, isMutable = false)
-
-
-    /**
-     * Get instance member traversing the hierarchy if needed. Its meaning is different for different objects.
-     */
-    fun getInstanceMemberOrNull(name: String): ObjRecord? {
-        members[name]?.let { return it }
-        allParentsSet.forEach { parent -> parent.getInstanceMemberOrNull(name)?.let { return it } }
-        return null
-    }
-
-    fun getInstanceMember(atPos: Pos, name: String): ObjRecord =
-        getInstanceMemberOrNull(name)
-            ?: throw ScriptError(atPos, "symbol doesn't exist: $name")
-}
-
-/**
- * Abstract class that must provide `iterator` method that returns [ObjIterator] instance.
- */
-val ObjIterable by lazy {
-    ObjClass("Iterable").apply {
-
-        addFn("toList") {
-            val result = mutableListOf<Obj>()
-            val iterator = thisObj.invokeInstanceMethod(this, "iterator")
-
-            while (iterator.invokeInstanceMethod(this, "hasNext").toBool())
-                result += iterator.invokeInstanceMethod(this, "next")
-
-
-//        val next = iterator.getMemberOrNull("next")!!
-//        val hasNext = iterator.getMemberOrNull("hasNext")!!
-//        while( hasNext.invoke(this, iterator).toBool() )
-//            result += next.invoke(this, iterator)
-            ObjList(result)
-        }
-
-    }
-}
-
-/**
- * Collection is an iterator with `size`]
- */
-val ObjCollection by lazy {
-    val i: ObjClass = ObjIterable
-    ObjClass("Collection", i).apply {
-        // it is not effective, but it is open:
-        addFn("contains", isOpen = true) {
-            val obj = args.firstAndOnly()
-            val it = thisObj.invokeInstanceMethod(this, "iterator")
-            while (it.invokeInstanceMethod(this, "hasNext").toBool()) {
-                if( obj.compareTo(this, it.invokeInstanceMethod(this, "next")) == 0 )
-                    return@addFn ObjTrue
-            }
-            ObjFalse
-        }
-
-    }
-}
-
-val ObjIterator by lazy { ObjClass("Iterator") }
-
-class ObjArrayIterator(val array: Obj) : Obj() {
-
-    override val objClass: ObjClass by lazy { type }
-
-    private var nextIndex = 0
-    private var lastIndex = 0
-
-    suspend fun init(context: Context) {
-        nextIndex = 0
-        lastIndex = array.invokeInstanceMethod(context, "size").toInt()
-        ObjVoid
-    }
-
-    companion object {
-        val type by lazy {
-            ObjClass("ArrayIterator", ObjIterator).apply {
-                addFn("next") {
-                    val self = thisAs<ObjArrayIterator>()
-                    if (self.nextIndex < self.lastIndex) {
-                        self.array.invokeInstanceMethod(this, "getAt", (self.nextIndex++).toObj())
-                    } else raiseError(ObjIterationFinishedException(this))
-                }
-                addFn("hasNext") {
-                    val self = thisAs<ObjArrayIterator>()
-                    if (self.nextIndex < self.lastIndex) ObjTrue else ObjFalse
-                }
-            }
-        }
-    }
-}
-
-
-val ObjArray by lazy {
-
-    /**
-     * Array abstract class is a [ObjCollection] with `getAt` method.
-     */
-    ObjClass("Array", ObjCollection).apply {
-        // we can create iterators using size/getat:
-
-        addFn("iterator") {
-            ObjArrayIterator(thisObj).also { it.init(this) }
-        }
-
-        addFn("contains", isOpen = true) {
-            val obj = args.firstAndOnly()
-            for( i in 0..< thisObj.invokeInstanceMethod(this, "size").toInt()) {
-                if( thisObj.getAt(this, i).compareTo(this, obj) == 0 ) return@addFn ObjTrue
-            }
-            ObjFalse
-        }
-
-        addFn("isample") { "ok".toObj() }
-    }
-}
-

library/src/commonMain/kotlin/net/sergeych/lyng/ObjList.kt

@@ -1,141 +0,0 @@
-package net.sergeych.lyng
-
-class ObjList(val list: MutableList<Obj> = mutableListOf()) : Obj() {
-
-    init {
-        for (p in objClass.parents)
-            parentInstances.add(p.defaultInstance())
-    }
-
-    override fun toString(): String = "[${
-        list.joinToString(separator = ", ") { it.inspect() }
-    }]"
-
-    fun normalize(context: Context, index: Int, allowisEndInclusive: Boolean = false): Int {
-        val i = if (index < 0) list.size + index else index
-        if (allowisEndInclusive && i == list.size) return i
-        if (i !in list.indices) context.raiseError("index $index out of bounds for size ${list.size}")
-        return i
-    }
-
-    override suspend fun getAt(context: Context, index: Int): Obj {
-        val i = normalize(context, index)
-        return list[i]
-    }
-
-    override suspend fun putAt(context: Context, index: Int, newValue: Obj) {
-        val i = normalize(context, index)
-        list[i] = newValue
-    }
-
-    override suspend fun compareTo(context: Context, other: Obj): Int {
-        if (other !is ObjList) return -2
-        val mySize = list.size
-        val otherSize = other.list.size
-        val commonSize = minOf(mySize, otherSize)
-        for (i in 0..<commonSize) {
-            if (list[i].compareTo(context, other.list[i]) != 0) {
-                return list[i].compareTo(context, other.list[i])
-            }
-        }
-        // equal so far, longer is greater:
-        return when {
-            mySize < otherSize -> -1
-            mySize > otherSize -> 1
-            else -> 0
-        }
-    }
-
-    override suspend fun plus(context: Context, other: Obj): Obj =
-        when {
-            other is ObjList ->
-                ObjList((list + other.list).toMutableList())
-
-            other.isInstanceOf(ObjIterable) -> {
-                val l = other.callMethod<ObjList>(context, "toList")
-                ObjList((list + l.list).toMutableList())
-            }
-
-            else ->
-                context.raiseError("'+': can't concatenate $this with $other")
-        }
-
-
-    override suspend fun plusAssign(context: Context, other: Obj): Obj {
-        // optimization
-        if (other is ObjList) {
-            list += other.list
-            return this
-        }
-        if (other.isInstanceOf(ObjIterable)) {
-            val otherList = other.invokeInstanceMethod(context, "toList") as ObjList
-            list += otherList.list
-        } else
-            list += other
-        return this
-    }
-
-    override suspend fun contains(context: Context, other: Obj): Boolean {
-        return list.contains(other)
-    }
-
-    override val objClass: ObjClass
-        get() = type
-
-    companion object {
-        val type = ObjClass("List", ObjArray).apply {
-
-            createField("size",
-                statement {
-                    (thisObj as ObjList).list.size.toObj()
-                }
-            )
-            addFn("getAt") {
-                requireExactCount(1)
-                thisAs<ObjList>().getAt(this, requiredArg<ObjInt>(0).value.toInt())
-            }
-            addFn("putAt") {
-                requireExactCount(2)
-                val newValue = args[1]
-                thisAs<ObjList>().putAt(this, requiredArg<ObjInt>(0).value.toInt(), newValue)
-                newValue
-            }
-            createField("add",
-                statement {
-                    val l = thisAs<ObjList>().list
-                    for (a in args) l.add(a)
-                    ObjVoid
-                }
-            )
-            createField("addAt",
-                statement {
-                    if (args.size < 2) raiseError("addAt takes 2+ arguments")
-                    val l = thisAs<ObjList>()
-                    var index = l.normalize(
-                        this, requiredArg<ObjInt>(0).value.toInt(),
-                        allowisEndInclusive = true
-                    )
-                    for (i in 1..<args.size) l.list.add(index++, args[i])
-                    ObjVoid
-                }
-            )
-            addFn("removeAt") {
-                val self = thisAs<ObjList>()
-                val start = self.normalize(this, requiredArg<ObjInt>(0).value.toInt())
-                if (args.size == 2) {
-                    val end = requireOnlyArg<ObjInt>().value.toInt()
-                    self.list.subList(start, self.normalize(this, end)).clear()
-                } else
-                    self.list.removeAt(start)
-                self
-            }
-            addFn("removeRangeInclusive") {
-                val self = thisAs<ObjList>()
-                val start = self.normalize(this, requiredArg<ObjInt>(0).value.toInt())
-                val end = self.normalize(this, requiredArg<ObjInt>(1).value.toInt()) + 1
-                self.list.subList(start, end).clear()
-                self
-            }
-        }
-    }
-}

library/src/commonMain/kotlin/net/sergeych/lyng/SymbolSpace.kt

@@ -1,13 +0,0 @@
-package net.sergeych.lyng
-
-
-
-class Symbols(
-    unitType: UnitType,
-    val name: String,
-    val x: TypeDecl
-) {
-    enum class UnitType {
-        Module, Function, Lambda
-    }
-}

library/src/commonMain/kotlin/net/sergeych/lyng/TypeDecl.kt

@@ -1,21 +0,0 @@
-package net.sergeych.lyng
-
-sealed class TypeDecl {
-    // ??
-    data class Fn(val argTypes: List<ArgsDeclaration.Item>, val retType: TypeDecl) : TypeDecl()
-    object Obj : TypeDecl()
-}
-
-/*
-To use in the compiler, we need symbol information when:
-
-- declaring a class: the only way to export its public/protected symbols is to know it in compiler time
-- importing a module: actually,  we cam try to do it in a more efficient way.
-
-Importing module:
-
-The moudule is efficiently a statement, that initializes it with all its symbols modifying some context.
-
-The thing is, we need only
-
- */

lyng/build.gradle.kts

@@ -29,11 +29,11 @@ kotlin {
     sourceSets {
         val commonMain by getting {
             dependencies {
-                implementation(project(":library"))
+                implementation(kotlin("stdlib-common"))
+                implementation(project(":lynglib"))
                 implementation(libs.okio)
-
                 implementation(libs.clikt)
-
+                implementation(kotlin("stdlib-common"))
                 // optional support for rendering markdown in help messages
 //                implementation(libs.clikt.markdown)
             }
@@ -42,9 +42,15 @@ kotlin {
             dependencies {
                 implementation(kotlin("test-common"))
                 implementation(kotlin("test-annotations-common"))
+                implementation(libs.kotlinx.coroutines.core)
                 implementation(libs.okio.fakefilesystem)
             }
         }
+//        val nativeMain by getting {
+//            dependencies {
+//                implementation(kotlin("stdlib-common"))
+//            }
+//        }
         val linuxX64Main by getting {
 
         }

lyng/src/commonMain/kotlin/Common.kt

@@ -17,11 +17,28 @@ import okio.use
 
 expect fun exit(code: Int)
 
+expect class ShellCommandExecutor {
+    fun executeCommand(command: String): CommandResult
+
+    companion object {
+        fun create(): ShellCommandExecutor
+    }
+}
+
+data class CommandResult(
+    val exitCode: Int,
+    val output: String,
+    val error: String
+)
+
 val baseContext = Context().apply {
     addFn("exit") {
         exit(requireOnlyArg<ObjInt>().toInt())
         ObjVoid
     }
+//    ObjString.type.addFn("shell") {
+//
+//    }
 }
 
 class Lyng(val launcher: (suspend () -> Unit) -> Unit) : CliktCommand() {
@@ -90,11 +107,16 @@ class Lyng(val launcher: (suspend () -> Unit) -> Unit) : CliktCommand() {
 }
 
 suspend fun executeFile(fileName: String) {
-    val text = FileSystem.SYSTEM.source(fileName.toPath()).use { fileSource ->
+    var text = FileSystem.SYSTEM.source(fileName.toPath()).use { fileSource ->
         fileSource.buffer().use { bs ->
             bs.readUtf8()
         }
     }
+    if( text.startsWith("#!") ) {
+        // skip shebang
+        val pos = text.indexOf('\n')
+        text = text.substring(pos + 1)
+    }
     processErrors {
         Compiler().compile(Source(fileName, text)).execute(baseContext)
     }

lyng/src/jvmMain/kotlin/Shell.jvm.kt

@@ -0,0 +1,23 @@
+@file:Suppress("EXPECT_ACTUAL_CLASSIFIERS_ARE_IN_BETA_WARNING")
+
+package net.sergeych
+
+// Alternative implementation for native targets
+actual class ShellCommandExecutor() {
+    actual fun executeCommand(command: String): CommandResult {
+        val process = ProcessBuilder("/bin/sh", "-c", command).start()
+        val exitCode = process.waitFor()
+        val output = process.inputStream.bufferedReader().readText()
+        val error = process.errorStream.bufferedReader().readText()
+
+        return CommandResult(
+            exitCode = exitCode,
+            output = output.trim(),
+            error = error.trim()
+        )
+    }
+
+    actual companion object {
+        actual fun create(): ShellCommandExecutor = ShellCommandExecutor()
+    }
+}

lyng/src/nativeMain/kotlin/Common.native.kt

@@ -1,7 +1,48 @@
+@file:OptIn(ExperimentalForeignApi::class, ExperimentalForeignApi::class, ExperimentalForeignApi::class)
+
 package net.sergeych
 
+import kotlinx.cinterop.*
+import platform.posix.fgets
+import platform.posix.pclose
+import platform.posix.popen
 import kotlin.system.exitProcess
 
+actual class ShellCommandExecutor() {
+    actual fun executeCommand(command: String): CommandResult {
+        val outputBuilder = StringBuilder()
+        val errorBuilder = StringBuilder()
+
+        val fp = popen(command, "r") ?: return CommandResult(
+            exitCode = -1,
+            output = "",
+            error = "Failed to execute command"
+        )
+
+        val buffer = ByteArray(4096)
+        while (true) {
+            val bytesRead = buffer.usePinned { pinned ->
+                fgets(pinned.addressOf(0), buffer.size.convert(), fp)
+            }
+            if (bytesRead == null) break
+            outputBuilder.append(bytesRead.toKString())
+        }
+
+        val status = pclose(fp)
+        val exitCode = if (status == 0) 0 else 1
+
+        return CommandResult(
+            exitCode = exitCode,
+            output = outputBuilder.toString().trim(),
+            error = errorBuilder.toString().trim()
+        )
+    }
+
+    actual companion object {
+        actual fun create(): ShellCommandExecutor = ShellCommandExecutor()
+    }
+}
+
 actual fun exit(code: Int) {
     exitProcess(code)
 }

lynglib/build.gradle.kts

@@ -1,11 +1,10 @@
 import com.codingfeline.buildkonfig.compiler.FieldSpec.Type.STRING
-import com.vanniktech.maven.publish.SonatypeHost
 import org.jetbrains.kotlin.gradle.ExperimentalKotlinGradlePluginApi
 import org.jetbrains.kotlin.gradle.ExperimentalWasmDsl
 import org.jetbrains.kotlin.gradle.dsl.JvmTarget
 
 group = "net.sergeych"
-version = "0.6.0-SNAPSHOT"
+version = "0.6.8-SNAPSHOT"
 
 buildscript {
     repositories {
@@ -20,9 +19,10 @@ buildscript {
 plugins {
     alias(libs.plugins.kotlinMultiplatform)
     alias(libs.plugins.androidLibrary)
-    alias(libs.plugins.vanniktech.mavenPublish)
+//    alias(libs.plugins.vanniktech.mavenPublish)
     kotlin("plugin.serialization") version "2.1.20"
     id("com.codingfeline.buildkonfig") version "0.17.1"
+    `maven-publish`
 }
 
 buildkonfig {
@@ -62,7 +62,7 @@ kotlin {
     sourceSets {
         all {
             languageSettings.optIn("kotlinx.coroutines.ExperimentalCoroutinesApi")
-            languageSettings.optIn("kotlin.contracts.ExperimentalContracts::class")
+            languageSettings.optIn("kotlin.contracts.ExperimentalContracts")
             languageSettings.optIn("kotlin.ExperimentalUnsignedTypes")
             languageSettings.optIn("kotlin.coroutines.DelicateCoroutinesApi")
         }
@@ -101,73 +101,54 @@ dependencies {
     implementation(libs.firebase.crashlytics.buildtools)
 }
 
-mavenPublishing {
-    publishToMavenCentral(SonatypeHost.CENTRAL_PORTAL)
-
-    signAllPublications()
-
-    coordinates(group.toString(), "library", version.toString())
-
-    pom {
-        name = "Lyng language"
-        description = "Kotlin-bound scripting loanguage"
-        inceptionYear = "2025"
-//        url = "https://sergeych.net"
-        licenses {
-            license {
-                name = "XXX"
-                url = "YYY"
-                distribution = "ZZZ"
+publishing {
+    val mavenToken by lazy {
+        File("${System.getProperty("user.home")}/.gitea_token").readText()
+    }
+    repositories {
+        maven {
+            credentials(HttpHeaderCredentials::class) {
+                name = "Authorization"
+                value = mavenToken
             }
-        }
-        developers {
-            developer {
-                id = "XXX"
-                name = "YYY"
-                url = "ZZZ"
+            url = uri("https://gitea.sergeych.net/api/packages/SergeychWorks/maven")
+            authentication {
+                create("Authorization", HttpHeaderAuthentication::class)
             }
         }
-        scm {
-            url = "XXX"
-            connection = "YYY"
-            developerConnection = "ZZZ"
-        }
     }
 }
+
+//mavenPublishing {
+//    publishToMavenCentral(SonatypeHost.CENTRAL_PORTAL)
 //
-//val projectVersion  by project.extra(provider {
-//    // Compute value lazily
-//    (version as String)
-//})
+//    signAllPublications()
 //
-//val generateBuildConfig by tasks.registering {
-//    // Declare outputs safely
-//    val outputDir = layout.buildDirectory.dir("generated/buildConfig/commonMain/kotlin")
-//    outputs.dir(outputDir)
+//    coordinates(group.toString(), "library", version.toString())
 //
-//    val version = projectVersion.get()
-//
-//    // Inputs: Version is tracked as an input
-//    inputs.property("version", version)
-//
-//    doLast {
-//        val packageName = "net.sergeych.lyng.buildconfig"
-//        val packagePath = packageName.replace('.', '/')
-//        val buildConfigFile = outputDir.get().file("$packagePath/BuildConfig.kt").asFile
-//
-//        buildConfigFile.parentFile?.mkdirs()
-//        buildConfigFile.writeText(
-//            """
-//            |package $packageName
-//            |
-//            |object BuildConfig {
-//            |    const val VERSION = "$version"
-//            |}
-//            """.trimMargin()
-//        )
+//    pom {
+//        name = "Lyng language"
+//        description = "Kotlin-bound scripting loanguage"
+//        inceptionYear = "2025"
+////        url = "https://sergeych.net"
+//        licenses {
+//            license {
+//                name = "XXX"
+//                url = "YYY"
+//                distribution = "ZZZ"
+//            }
+//        }
+//        developers {
+//            developer {
+//                id = "XXX"
+//                name = "YYY"
+//                url = "ZZZ"
+//            }
+//        }
+//        scm {
+//            url = "XXX"
+//            connection = "YYY"
+//            developerConnection = "ZZZ"
+//        }
 //    }
 //}
-//
-//tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile>().configureEach {
-//    dependsOn(generateBuildConfig)
-//}

lynglib/src/commonMain/kotlin/net/sergeych/lyng/AppliedContext.kt

@@ -0,0 +1,17 @@
+package net.sergeych.lyng
+
+/**
+ * Special version of the [Context] used to `apply` new this object to
+ * _parent context property.
+ *
+ * @param _parent context to apply to
+ * @param args arguments for the new context
+ * @param appliedContext the new context to apply, it will have lower priority except for `this` which
+ *      will be reset by appliedContext's `this`.
+ */
+class AppliedContext(_parent: Context, args: Arguments, val appliedContext: Context)
+    : Context(_parent, args, appliedContext.pos, appliedContext.thisObj) {
+    override fun get(name: String): ObjRecord? =
+        if (name == "this") thisObj.asReadonly
+        else super.get(name) ?: appliedContext[name]
+}

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ArgsDeclaration.kt

@@ -56,7 +56,7 @@ data class ArgsDeclaration(val params: List<Item>, val endTokenType: Token.Type)
                     else -> {
                         println("callArgs: ${callArgs.joinToString()}")
                         println("tailBlockMode: ${arguments.tailBlockMode}")
-                        context.raiseArgumentError("too few arguments for the call")
+                        context.raiseIllegalArgument("too few arguments for the call")
                     }
                 }
                 assign(a, value)
@@ -77,7 +77,7 @@ data class ArgsDeclaration(val params: List<Item>, val endTokenType: Token.Type)
                     }
 
                     a.defaultValue != null -> a.defaultValue.execute(context)
-                    else -> context.raiseArgumentError("too few arguments for the call")
+                    else -> context.raiseIllegalArgument("too few arguments for the call")
                 }
                 assign(a, value)
                 i--
@@ -98,7 +98,7 @@ data class ArgsDeclaration(val params: List<Item>, val endTokenType: Token.Type)
             processEllipsis(leftIndex, end)
         } else {
             if (leftIndex < callArgs.size)
-                context.raiseArgumentError("too many arguments for the call")
+                context.raiseIllegalArgument("too many arguments for the call")
         }
     }
 
@@ -110,7 +110,7 @@ data class ArgsDeclaration(val params: List<Item>, val endTokenType: Token.Type)
      */
     data class Item(
         val name: String,
-        val type: TypeDecl = TypeDecl.Obj,
+        val type: TypeDecl = TypeDecl.TypeAny,
         val pos: Pos = Pos.builtIn,
         val isEllipsis: Boolean = false,
         /**

lynglib/src/commonMain/kotlin/net/sergeych/lyng/Arguments.kt

@@ -28,11 +28,20 @@ suspend fun Collection<ParsedArgument>.toArguments(context: Context,tailBlockMod
 
 data class Arguments(val list: List<Obj>,val tailBlockMode: Boolean = false) : List<Obj> by list {
 
+    constructor(vararg values: Obj) : this(values.toList())
+
     fun firstAndOnly(pos: Pos = Pos.UNKNOWN): Obj {
         if (list.size != 1) throw ScriptError(pos, "expected one argument, got ${list.size}")
         return list.first()
     }
 
+    /**
+     * Convert to list of kotlin objects, see [Obj.toKotlin].
+     */
+    suspend fun toKotlinList(context: Context): List<Any?> {
+        return list.map { it.toKotlin(context) }
+    }
+
     companion object {
         val EMPTY = Arguments(emptyList())
         fun from(values: Collection<Obj>) = Arguments(values.toList())

lynglib/src/commonMain/kotlin/net/sergeych/lyng/Compiler.kt

@@ -59,7 +59,7 @@ class Compiler(
                         parseBlock(cc)
                 }
 
-                Token.Type.RBRACE -> {
+                Token.Type.RBRACE, Token.Type.RBRACKET -> {
                     cc.previous()
                     return null
                 }
@@ -121,7 +121,8 @@ class Compiler(
                     operand = Accessor { op.getter(it).value.logicalNot(it).asReadonly }
                 }
 
-                Token.Type.DOT -> {
+                Token.Type.DOT, Token.Type.NULL_COALESCE -> {
+                    val isOptional = t.type == Token.Type.NULL_COALESCE
                     operand?.let { left ->
                         // dotcall: calling method on the operand, if next is ID, "("
                         var isCall = false
@@ -138,34 +139,41 @@ class Compiler(
                                     operand = Accessor { context ->
                                         context.pos = next.pos
                                         val v = left.getter(context).value
-                                        ObjRecord(
-                                            v.invokeInstanceMethod(
-                                                context,
-                                                next.value,
-                                                args.toArguments(context, false)
-                                            ), isMutable = false
-                                        )
+                                        if (v == ObjNull && isOptional)
+                                            ObjNull.asReadonly
+                                        else
+                                            ObjRecord(
+                                                v.invokeInstanceMethod(
+                                                    context,
+                                                    next.value,
+                                                    args.toArguments(context, false)
+                                                ), isMutable = false
+                                            )
                                     }
                                 }
 
-                                Token.Type.LBRACE -> {
+
+                                Token.Type.LBRACE, Token.Type.NULL_COALESCE_BLOCKINVOKE -> {
+//                                    isOptional = nt.type == Token.Type.NULL_COALESCE_BLOCKINVOKE
                                     // single lambda arg, like assertTrows { ... }
                                     cc.next()
                                     isCall = true
                                     val lambda =
-                                        parseExpression(cc) ?: throw ScriptError(t.pos, "expected valid lambda here")
+                                        parseLambdaExpression(cc)
                                     println(cc.current())
-                                    cc.skipTokenOfType(Token.Type.RBRACE)
                                     operand = Accessor { context ->
                                         context.pos = next.pos
                                         val v = left.getter(context).value
-                                        ObjRecord(
-                                            v.invokeInstanceMethod(
-                                                context,
-                                                next.value,
-                                                Arguments(listOf(lambda), true)
-                                            ), isMutable = false
-                                        )
+                                        if (v == ObjNull && isOptional)
+                                            ObjNull.asReadonly
+                                        else
+                                            ObjRecord(
+                                                v.invokeInstanceMethod(
+                                                    context,
+                                                    next.value,
+                                                    Arguments(listOf(lambda.getter(context).value), true)
+                                                ), isMutable = false
+                                            )
                                     }
                                 }
 
@@ -174,25 +182,30 @@ class Compiler(
                         }
                         if (!isCall) {
                             operand = Accessor({ context ->
-                                left.getter(context).value.readField(context, next.value)
+                                val x = left.getter(context).value
+                                if (x == ObjNull && isOptional) ObjNull.asReadonly
+                                else x.readField(context, next.value)
                             }) { cc, newValue ->
                                 left.getter(cc).value.writeField(cc, next.value, newValue)
                             }
                         }
-                    } ?: throw ScriptError(t.pos, "Expecting expression before dot")
+                    }
+
+                        ?: throw ScriptError(t.pos, "Expecting expression before dot")
                 }
 
                 Token.Type.COLONCOLON -> {
                     operand = parseScopeOperator(operand, cc)
                 }
 
-                Token.Type.LPAREN -> {
+                Token.Type.LPAREN, Token.Type.NULL_COALESCE_INVOKE -> {
                     operand?.let { left ->
                         // this is function call from <left>
                         operand = parseFunctionCall(
                             cc,
                             left,
                             false,
+                            t.type == Token.Type.NULL_COALESCE_INVOKE
                         )
                     } ?: run {
                         // Expression in parentheses
@@ -205,15 +218,17 @@ class Compiler(
                     }
                 }
 
-                Token.Type.LBRACKET -> {
+                Token.Type.LBRACKET, Token.Type.NULL_COALESCE_INDEX -> {
                     operand?.let { left ->
                         // array access
+                        val isOptional = t.type == Token.Type.NULL_COALESCE_INDEX
                         val index = parseStatement(cc) ?: throw ScriptError(t.pos, "Expecting index expression")
                         cc.skipTokenOfType(Token.Type.RBRACKET, "missing ']' at the end of the list literal")
                         operand = Accessor({ cxt ->
-                            val i = (index.execute(cxt) as? ObjInt)?.value?.toInt()
-                                ?: cxt.raiseError("index must be integer")
-                            left.getter(cxt).value.getAt(cxt, i).asMutable
+                            val i = index.execute(cxt)
+                            val x = left.getter(cxt).value
+                            if (x == ObjNull && isOptional) ObjNull.asReadonly
+                            else x.getAt(cxt, i).asMutable
                         }) { cxt, newValue ->
                             val i = (index.execute(cxt) as? ObjInt)?.value?.toInt()
                                 ?: cxt.raiseError("index must be integer")
@@ -324,10 +339,10 @@ class Compiler(
                 }
 
                 Token.Type.DOTDOT, Token.Type.DOTDOTLT -> {
-                    // closed-range operator
+                    // range operator
                     val isEndInclusive = t.type == Token.Type.DOTDOT
                     val left = operand
-                    val right = parseStatement(cc)
+                    val right = parseExpression(cc)
                     operand = Accessor {
                         ObjRange(
                             left?.getter?.invoke(it)?.value ?: ObjNull,
@@ -337,18 +352,27 @@ class Compiler(
                     }
                 }
 
-                Token.Type.LBRACE -> {
+                Token.Type.LBRACE, Token.Type.NULL_COALESCE_BLOCKINVOKE -> {
                     operand = operand?.let { left ->
                         cc.previous()
-                        parseFunctionCall(cc, left, blockArgument = true)
+                        parseFunctionCall(
+                            cc,
+                            left,
+                            blockArgument = true,
+                            t.type == Token.Type.NULL_COALESCE_BLOCKINVOKE
+                        )
                     } ?: parseLambdaExpression(cc)
                 }
 
+                Token.Type.RBRACKET, Token.Type.RPAREN -> {
+                    cc.previous()
+                    return operand
+                }
 
                 else -> {
                     cc.previous()
                     operand?.let { return it }
-                    operand = parseAccessor(cc) ?: throw ScriptError(t.pos, "Expecting expression")
+                    operand = parseAccessor(cc) ?: return null //throw ScriptError(t.pos, "Expecting expression")
                 }
             }
         }
@@ -363,13 +387,14 @@ class Compiler(
         val argsDeclaration = parseArgsDeclaration(cc)
         if (argsDeclaration != null && argsDeclaration.endTokenType != Token.Type.ARROW)
             throw ScriptError(startPos, "lambda must have either valid arguments declaration with '->' or no arguments")
-        val pos = cc.currentPos()
+
         val body = parseBlock(cc, skipLeadingBrace = true)
 
         var closure: Context? = null
 
         val callStatement = statement {
-            val context = closure!!.copy(pos, args)
+            // and the source closure of the lambda which might have other thisObj.
+            val context = AppliedContext(closure!!, args, this)
             if (argsDeclaration == null) {
                 // no args: automatic var 'it'
                 val l = args.list
@@ -535,11 +560,11 @@ class Compiler(
     }
 
     private fun parseTypeDeclaration(cc: CompilerContext): TypeDecl {
-        val result = TypeDecl.Obj
-        cc.ifNextIs(Token.Type.COLON) {
-            TODO("parse type declaration here")
-        }
-        return result
+        return if (cc.skipTokenOfType(Token.Type.COLON, isOptional = true)) {
+            val tt = cc.requireToken(Token.Type.ID, "type name or type expression required")
+            val isNullable = cc.skipTokenOfType(Token.Type.QUESTION, isOptional = true)
+            TypeDecl.Simple(tt.value, isNullable)
+        } else TypeDecl.TypeAny
     }
 
     /**
@@ -565,6 +590,8 @@ class Compiler(
                     cc.previous()
                     parseExpression(cc)?.let { args += ParsedArgument(it, t.pos) }
                         ?: throw ScriptError(t.pos, "Expecting arguments list")
+                    if (cc.current().type == Token.Type.COLON)
+                        parseTypeDeclaration(cc)
                     // Here should be a valid termination:
                 }
             }
@@ -590,7 +617,12 @@ class Compiler(
     }
 
 
-    private fun parseFunctionCall(cc: CompilerContext, left: Accessor, blockArgument: Boolean): Accessor {
+    private fun parseFunctionCall(
+        cc: CompilerContext,
+        left: Accessor,
+        blockArgument: Boolean,
+        isOptional: Boolean
+    ): Accessor {
         // insofar, functions always return lvalue
         var detectedBlockArgument = blockArgument
         val args = if (blockArgument) {
@@ -607,6 +639,7 @@ class Compiler(
 
         return Accessor { context ->
             val v = left.getter(context)
+            if (v.value == ObjNull && isOptional) return@Accessor v.value.asReadonly
             v.value.callOn(
                 context.copy(
                     context.pos,
@@ -693,7 +726,7 @@ class Compiler(
     }
 
     /**
-     * Parse keyword-starting statenment.
+     * Parse keyword-starting statement.
      * @return parsed statement or null if, for example. [id] is not among keywords
      */
     private fun parseKeywordStatement(id: Token, cc: CompilerContext): Statement? = when (id.value) {
@@ -704,7 +737,6 @@ class Compiler(
         "for" -> parseForStatement(cc)
         "break" -> parseBreakStatement(id.pos, cc)
         "continue" -> parseContinueStatement(id.pos, cc)
-        "fn", "fun" -> parseFunctionDeclaration(cc)
         "if" -> parseIfStatement(cc)
         "class" -> parseClassDeclaration(cc, false)
         "try" -> parseTryStatement(cc)
@@ -713,11 +745,16 @@ class Compiler(
         else -> {
             // triples
             cc.previous()
+            val isExtern = cc.skipId("extern")
             when {
-                cc.matchQualifiers("fun", "private") -> parseFunctionDeclaration(cc, Visibility.Private)
-                cc.matchQualifiers("fn", "private") -> parseFunctionDeclaration(cc, Visibility.Private)
-                cc.matchQualifiers("fun", "open") -> parseFunctionDeclaration(cc, isOpen = true)
-                cc.matchQualifiers("fn", "open") -> parseFunctionDeclaration(cc, isOpen = true)
+                cc.matchQualifiers("fun", "private") -> parseFunctionDeclaration(cc, Visibility.Private, isExtern)
+                cc.matchQualifiers("fn", "private") -> parseFunctionDeclaration(cc, Visibility.Private, isExtern)
+                cc.matchQualifiers("fun", "open") -> parseFunctionDeclaration(cc, isOpen = true, isExtern = isExtern)
+                cc.matchQualifiers("fn", "open") -> parseFunctionDeclaration(cc, isOpen = true, isExtern = isExtern)
+
+                cc.matchQualifiers("fun") -> parseFunctionDeclaration(cc, isOpen = false, isExtern = isExtern)
+                cc.matchQualifiers("fn") -> parseFunctionDeclaration(cc, isOpen = false, isExtern = isExtern)
+
                 cc.matchQualifiers("val", "private") -> parseVarDeclaration(false, Visibility.Private, cc)
                 cc.matchQualifiers("var", "private") -> parseVarDeclaration(true, Visibility.Private, cc)
                 cc.matchQualifiers("val", "open") -> parseVarDeclaration(false, Visibility.Private, cc, true)
@@ -1087,7 +1124,7 @@ class Compiler(
                     var breakCaught = false
 
                     if (size > 0) {
-                        var current = runCatching { sourceObj.getAt(forContext, 0) }
+                        var current = runCatching { sourceObj.getAt(forContext, ObjInt(0)) }
                             .getOrElse {
                                 throw ScriptError(
                                     tOp.pos,
@@ -1114,7 +1151,7 @@ class Compiler(
                                 }
                             } else result = body.execute(forContext)
                             if (++index >= size) break
-                            current = sourceObj.getAt(forContext, index)
+                            current = sourceObj.getAt(forContext, ObjInt(index.toLong()))
                         }
                     }
                     if (!breakCaught && elseStatement != null) {
@@ -1388,29 +1425,35 @@ class Compiler(
     }
 
     private fun parseFunctionDeclaration(
-        tokens: CompilerContext,
+        cc: CompilerContext,
         visibility: Visibility = Visibility.Public,
-        @Suppress("UNUSED_PARAMETER") isOpen: Boolean = false
+        @Suppress("UNUSED_PARAMETER") isOpen: Boolean = false,
+        isExtern: Boolean = false
     ): Statement {
-        var t = tokens.next()
+        var t = cc.next()
         val start = t.pos
         val name = if (t.type != Token.Type.ID)
             throw ScriptError(t.pos, "Expected identifier after 'fn'")
         else t.value
 
-        t = tokens.next()
+        t = cc.next()
         if (t.type != Token.Type.LPAREN)
             throw ScriptError(t.pos, "Bad function definition: expected '(' after 'fn ${name}'")
 
-        val argsDeclaration = parseArgsDeclaration(tokens)
+        val argsDeclaration = parseArgsDeclaration(cc)
         if (argsDeclaration == null || argsDeclaration.endTokenType != Token.Type.RPAREN)
             throw ScriptError(
                 t.pos,
                 "Bad function definition: expected valid argument declaration or () after 'fn ${name}'"
             )
 
+        if (cc.current().type == Token.Type.COLON) parseTypeDeclaration(cc)
+
         // Here we should be at open body
-        val fnStatements = parseBlock(tokens)
+        val fnStatements = if (isExtern)
+            statement { raiseError("extern function not provided: $name") }
+        else
+            parseBlock(cc)
 
         var closure: Context? = null
 
@@ -1586,6 +1629,8 @@ class Compiler(
             // bitwise or 2
             // bitwise and 3
             // equality/ne 4
+            Operator.simple(Token.Type.EQARROW, ++lastPrty) { c, a, b -> ObjMapEntry(a, b) },
+            //
             Operator.simple(Token.Type.EQ, ++lastPrty) { c, a, b -> ObjBool(a.compareTo(c, b) == 0) },
             Operator.simple(Token.Type.NEQ, lastPrty) { c, a, b -> ObjBool(a.compareTo(c, b) != 0) },
             Operator.simple(Token.Type.REF_EQ, lastPrty) { _, a, b -> ObjBool(a === b) },
@@ -1600,6 +1645,9 @@ class Compiler(
             Operator.simple(Token.Type.NOTIN, lastPrty) { c, a, b -> ObjBool(!b.contains(c, a)) },
             Operator.simple(Token.Type.IS, lastPrty) { c, a, b -> ObjBool(a.isInstanceOf(b)) },
             Operator.simple(Token.Type.NOTIS, lastPrty) { c, a, b -> ObjBool(!a.isInstanceOf(b)) },
+
+            Operator.simple(Token.Type.ELVIS, ++lastPrty) { c, a, b -> if (a == ObjNull) b else a },
+
             // shuttle <=> 6
             Operator.simple(Token.Type.SHUTTLE, ++lastPrty) { c, a, b ->
                 ObjInt(a.compareTo(c, b).toLong())
@@ -1632,7 +1680,7 @@ class Compiler(
          * The keywords that stop processing of expression term
          */
         val stopKeywords =
-            setOf("do", "break", "continue", "return", "if", "when", "do", "while", "for", "class", "struct")
+            setOf("do", "break", "continue", "return", "if", "when", "do", "while", "for", "class")
     }
 }
 

lynglib/src/commonMain/kotlin/net/sergeych/lyng/CompilerContext.kt

@@ -53,6 +53,20 @@ internal class CompilerContext(val tokens: List<Token>) {
 
     fun currentPos(): Pos = tokens[currentIndex].pos
 
+    /**
+     * If the next token is identifier `name`, skip it and return `true`.
+     * else leave where it is and return `false`
+     */
+    fun skipId(name: String): Boolean {
+        current().let { t ->
+            if( t.type == Token.Type.ID && t.value == name ) {
+                next()
+                return true
+            }
+        }
+        return false
+    }
+
     /**
      * Skips next token if its type is `tokenType`, returns `true` if so.
      * @param errorMessage message to throw if next token is not `tokenType`

lynglib/src/commonMain/kotlin/net/sergeych/lyng/Context.kt

@@ -1,10 +1,10 @@
 package net.sergeych.lyng
 
-class Context(
+open class Context(
     val parent: Context?,
     val args: Arguments = Arguments.EMPTY,
     var pos: Pos = Pos.builtIn,
-    val thisObj: Obj = ObjVoid,
+    var thisObj: Obj = ObjVoid,
     var skipContextCreation: Boolean = false,
 ) {
     constructor(
@@ -16,14 +16,18 @@ class Context(
     fun raiseNotImplemented(what: String = "operation"): Nothing = raiseError("$what is not implemented")
 
     @Suppress("unused")
-    fun raiseNPE(): Nothing = raiseError(ObjNullPointerException(this))
+    fun raiseNPE(): Nothing = raiseError(ObjNullReferenceException(this))
 
     @Suppress("unused")
     fun raiseIndexOutOfBounds(message: String = "Index out of bounds"): Nothing =
         raiseError(ObjIndexOutOfBoundsException(this, message))
 
     @Suppress("unused")
-    fun raiseArgumentError(message: String = "Illegal argument error"): Nothing =
+    fun raiseIllegalArgument(message: String = "Illegal argument error"): Nothing =
+        raiseError(ObjIllegalArgumentException(this, message))
+
+    @Suppress("unused")
+    fun raiseNoSuchElement(message: String = "No such element"): Nothing =
         raiseError(ObjIllegalArgumentException(this, message))
 
     fun raiseClassCastError(msg: String): Nothing = raiseError(ObjClassCastException(this, msg))
@@ -63,9 +67,12 @@ class Context(
 
     internal val objects = mutableMapOf<String, ObjRecord>()
 
-    operator fun get(name: String): ObjRecord? =
-        objects[name]
-            ?: parent?.get(name)
+    open operator fun get(name: String): ObjRecord? =
+        if (name == "this") thisObj.asReadonly
+        else {
+            objects[name]
+                ?: parent?.get(name)
+        }
 
     fun copy(pos: Pos, args: Arguments = Arguments.EMPTY, newThisObj: Obj? = null): Context =
         Context(this, args, pos, newThisObj ?: thisObj)
@@ -119,5 +126,4 @@ class Context(
 
     fun containsLocal(name: String): Boolean = name in objects
 
-
 }

lynglib/src/commonMain/kotlin/net/sergeych/lyng/Obj.kt

@@ -42,6 +42,9 @@ data class Accessor(
 }
 
 open class Obj {
+
+    val isNull by lazy { this === ObjNull }
+
     var isFrozen: Boolean = false
 
     private val monitor = Mutex()
@@ -61,7 +64,11 @@ open class Obj {
      */
     open fun byValueCopy(): Obj = this
 
-    fun isInstanceOf(someClass: Obj) = someClass === objClass || objClass.allParentsSet.contains(someClass)
+    @Suppress("SuspiciousEqualsCombination")
+    fun isInstanceOf(someClass: Obj) = someClass === objClass ||
+            objClass.allParentsSet.contains(someClass) ||
+            someClass == rootObjectType
+
 
     suspend fun invokeInstanceMethod(context: Context, name: String, vararg args: Obj): Obj =
         invokeInstanceMethod(context, name, Arguments(args.toList()))
@@ -100,16 +107,7 @@ open class Obj {
      * Class of the object: definition of member functions (top-level), etc.
      * Note that using lazy allows to avoid endless recursion here
      */
-    open val objClass: ObjClass by lazy {
-        ObjClass("Obj").apply {
-            addFn("toString") {
-                thisObj.asStr
-            }
-            addFn("contains") {
-                ObjBool(thisObj.contains(this, args.firstAndOnly()))
-            }
-        }
-    }
+    open val objClass: ObjClass = rootObjectType
 
     open suspend fun plus(context: Context, other: Obj): Obj {
         context.raiseNotImplemented()
@@ -176,6 +174,13 @@ open class Obj {
         context.raiseNotImplemented()
     }
 
+    /**
+     * Convert Lyng object to its Kotlin counterpart
+     */
+    open suspend fun toKotlin(context: Context): Any? {
+        return toString()
+    }
+
     fun willMutate(context: Context) {
         if (isFrozen) context.raiseError("attempt to mutate frozen object")
     }
@@ -201,7 +206,7 @@ open class Obj {
         if (field.isMutable) field.value = newValue else context.raiseError("can't assign to read-only field: $name")
     }
 
-    open suspend fun getAt(context: Context, index: Int): Obj {
+    open suspend fun getAt(context: Context, index: Obj): Obj {
         context.raiseNotImplemented("indexing")
     }
 
@@ -243,7 +248,33 @@ open class Obj {
 
 
     companion object {
-        inline fun <reified T> from(obj: T): Obj {
+
+        val rootObjectType = ObjClass("Obj").apply {
+                addFn("toString") {
+                    thisObj.asStr
+                }
+                addFn("contains") {
+                    ObjBool(thisObj.contains(this, args.firstAndOnly()))
+                }
+                // utilities
+                addFn("let") {
+                    args.firstAndOnly().callOn(copy(Arguments(thisObj)))
+                }
+                addFn("apply") {
+                    val newContext = ( thisObj as? ObjInstance)?.instanceContext ?: this
+                    args.firstAndOnly()
+                        .callOn(newContext)
+                    thisObj
+                }
+                addFn("also") {
+                    args.firstAndOnly().callOn(copy(Arguments(thisObj)))
+                    thisObj
+                }
+            }
+
+
+        inline fun from(obj: Any?): Obj {
+            @Suppress("UNCHECKED_CAST")
             return when (obj) {
                 is Obj -> obj
                 is Double -> ObjReal(obj)
@@ -253,8 +284,15 @@ open class Obj {
                 is String -> ObjString(obj)
                 is CharSequence -> ObjString(obj.toString())
                 is Boolean -> ObjBool(obj)
+                is Set<*> -> ObjSet((obj as Set<Obj>).toMutableSet())
                 Unit -> ObjVoid
                 null -> ObjNull
+                is Iterator<*> -> ObjKotlinIterator(obj)
+                is Map.Entry<*, *> -> {
+                    obj as MutableMap.MutableEntry<Obj, Obj>
+                    ObjMapEntry(obj.key, obj.value)
+                }
+
                 else -> throw IllegalArgumentException("cannot convert to Obj: $obj")
             }
         }
@@ -289,7 +327,31 @@ object ObjNull : Obj() {
         return other is ObjNull || other == null
     }
 
+    override suspend fun readField(context: Context, name: String): ObjRecord {
+        context.raiseNPE()
+    }
+
+    override suspend fun invokeInstanceMethod(context: Context, name: String, args: Arguments): Obj {
+        context.raiseNPE()
+    }
+
+    override suspend fun getAt(context: Context, index: Obj): Obj {
+        context.raiseNPE()
+    }
+
+    override suspend fun putAt(context: Context, index: Int, newValue: Obj) {
+        context.raiseNPE()
+    }
+
+    override suspend fun callOn(context: Context): Obj {
+        context.raiseNPE()
+    }
+
     override fun toString(): String = "null"
+
+    override suspend fun toKotlin(context: Context): Any? {
+        return null
+    }
 }
 
 interface Numeric {
@@ -330,7 +392,12 @@ data class ObjNamespace(val name: String) : Obj() {
 }
 
 open class ObjException(exceptionClass: ExceptionClass, val context: Context, val message: String) : Obj() {
-    constructor(name: String,context: Context, message: String) : this(getOrCreateExceptionClass(name), context, message)
+    constructor(name: String, context: Context, message: String) : this(
+        getOrCreateExceptionClass(name),
+        context,
+        message
+    )
+
     constructor(context: Context, message: String) : this(Root, context, message)
 
     fun raise(): Nothing {
@@ -345,13 +412,15 @@ open class ObjException(exceptionClass: ExceptionClass, val context: Context, va
 
     companion object {
 
-        class ExceptionClass(val name: String,vararg parents: ObjClass) : ObjClass(name, *parents) {
+        class ExceptionClass(val name: String, vararg parents: ObjClass) : ObjClass(name, *parents) {
             override suspend fun callOn(context: Context): Obj {
                 val message = context.args.getOrNull(0)?.toString() ?: name
                 return ObjException(this, context, message)
             }
+
             override fun toString(): String = "ExceptionClass[$name]@${hashCode().encodeToHex()}"
         }
+
         val Root = ExceptionClass("Throwable").apply {
             addConst("message", statement {
                 (thisObj as ObjException).message.toObj()
@@ -383,11 +452,12 @@ open class ObjException(exceptionClass: ExceptionClass, val context: Context, va
             context.addConst("Exception", Root)
             existingErrorClasses["Exception"] = Root
             for (name in listOf(
-                "NullPointerException",
+                "NullReferenceException",
                 "AssertionFailedException",
                 "ClassCastException",
                 "IndexOutOfBoundsException",
                 "IllegalArgumentException",
+                "NoSuchElementException",
                 "IllegalAssignmentException",
                 "SymbolNotDefinedException",
                 "IterationEndException",
@@ -400,7 +470,7 @@ open class ObjException(exceptionClass: ExceptionClass, val context: Context, va
     }
 }
 
-class ObjNullPointerException(context: Context) : ObjException("NullPointerException", context, "object is null")
+class ObjNullReferenceException(context: Context) : ObjException("NullReferenceException", context, "object is null")
 
 class ObjAssertionFailedException(context: Context, message: String) :
     ObjException("AssertionFailedException", context, message)
@@ -412,8 +482,12 @@ class ObjIndexOutOfBoundsException(context: Context, message: String = "index ou
 class ObjIllegalArgumentException(context: Context, message: String = "illegal argument") :
     ObjException("IllegalArgumentException", context, message)
 
+@Suppress("unused")
+class ObjNoSuchElementException(context: Context, message: String = "no such element") :
+    ObjException("IllegalArgumentException", context, message)
+
 class ObjIllegalAssignmentException(context: Context, message: String = "illegal assignment") :
-    ObjException("IllegalAssignmentException", context, message)
+    ObjException("NoSuchElementException", context, message)
 
 class ObjSymbolNotDefinedException(context: Context, message: String = "symbol is not defined") :
     ObjException("SymbolNotDefinedException", context, message)

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjArray.kt

@@ -0,0 +1,38 @@
+package net.sergeych.lyng
+
+val ObjArray by lazy {
+
+    /**
+     * Array abstract class is a [ObjCollection] with `getAt` method.
+     */
+    ObjClass("Array", ObjCollection).apply {
+        // we can create iterators using size/getat:
+
+        addFn("iterator") {
+            ObjArrayIterator(thisObj).also { it.init(this) }
+        }
+
+        addFn("contains", isOpen = true) {
+            val obj = args.firstAndOnly()
+            for (i in 0..<thisObj.invokeInstanceMethod(this, "size").toInt()) {
+                if (thisObj.getAt(this, ObjInt(i.toLong())).compareTo(this, obj) == 0) return@addFn ObjTrue
+            }
+            ObjFalse
+        }
+
+        addFn("last") {
+            thisObj.invokeInstanceMethod(
+                this,
+                "getAt",
+                (thisObj.invokeInstanceMethod(this, "size").toInt() - 1).toObj()
+            )
+        }
+
+        addFn("lastIndex") { (thisObj.invokeInstanceMethod(this, "size").toInt() - 1).toObj() }
+
+        addFn("indices") {
+            ObjRange(0.toObj(), thisObj.invokeInstanceMethod(this, "size"), false)
+        }
+
+    }
+}

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjArrayIterator.kt

@@ -0,0 +1,32 @@
+package net.sergeych.lyng
+
+class ObjArrayIterator(val array: Obj) : Obj() {
+
+    override val objClass: ObjClass by lazy { type }
+
+    private var nextIndex = 0
+    private var lastIndex = 0
+
+    suspend fun init(context: Context) {
+        nextIndex = 0
+        lastIndex = array.invokeInstanceMethod(context, "size").toInt()
+        ObjVoid
+    }
+
+    companion object {
+        val type by lazy {
+            ObjClass("ArrayIterator", ObjIterator).apply {
+                addFn("next") {
+                    val self = thisAs<ObjArrayIterator>()
+                    if (self.nextIndex < self.lastIndex) {
+                        self.array.invokeInstanceMethod(this, "getAt", (self.nextIndex++).toObj())
+                    } else raiseError(ObjIterationFinishedException(this))
+                }
+                addFn("hasNext") {
+                    val self = thisAs<ObjArrayIterator>()
+                    if (self.nextIndex < self.lastIndex) ObjTrue else ObjFalse
+                }
+            }
+        }
+    }
+}

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjBool.kt

@@ -18,6 +18,10 @@ data class ObjBool(val value: Boolean) : Obj() {
 
     override suspend fun logicalOr(context: Context, other: Obj): Obj = ObjBool(value || other.toBool())
 
+    override suspend fun toKotlin(context: Context): Any {
+        return value
+    }
+
     companion object {
         val type = ObjClass("Bool")
     }

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjClass.kt

@@ -0,0 +1,73 @@
+package net.sergeych.lyng
+
+val ObjClassType by lazy { ObjClass("Class") }
+
+open class ObjClass(
+    val className: String,
+    vararg val parents: ObjClass,
+) : Obj() {
+
+    var instanceConstructor: Statement? = null
+
+    val allParentsSet: Set<ObjClass> =
+        parents.flatMap {
+            listOf(it) + it.allParentsSet
+        }.toMutableSet()
+
+    override val objClass: ObjClass by lazy { ObjClassType }
+
+    // members: fields most often
+    private val members = mutableMapOf<String, ObjRecord>()
+
+    override fun toString(): String = className
+
+    override suspend fun compareTo(context: Context, other: Obj): Int = if (other === this) 0 else -1
+
+    override suspend fun callOn(context: Context): Obj {
+        val instance = ObjInstance(this)
+        instance.instanceContext = context.copy(newThisObj = instance,args = context.args)
+        if (instanceConstructor != null) {
+            instanceConstructor!!.execute(instance.instanceContext)
+        }
+        return instance
+    }
+
+    fun defaultInstance(): Obj = object : Obj() {
+        override val objClass: ObjClass = this@ObjClass
+    }
+
+    fun createField(
+        name: String,
+        initialValue: Obj,
+        isMutable: Boolean = false,
+        visibility: Visibility = Visibility.Public,
+        pos: Pos = Pos.builtIn
+    ) {
+        val existing = members[name] ?: allParentsSet.firstNotNullOfOrNull { it.members[name] }
+        if( existing?.isMutable == false)
+            throw ScriptError(pos, "$name is already defined in $objClass or one of its supertypes")
+        members[name] = ObjRecord(initialValue, isMutable, visibility)
+    }
+
+    fun addFn(name: String, isOpen: Boolean = false, code: suspend Context.() -> Obj) {
+        createField(name, statement { code() }, isOpen)
+    }
+
+    fun addConst(name: String, value: Obj) = createField(name, value, isMutable = false)
+
+
+    /**
+     * Get instance member traversing the hierarchy if needed. Its meaning is different for different objects.
+     */
+    fun getInstanceMemberOrNull(name: String): ObjRecord? {
+        members[name]?.let { return it }
+        allParentsSet.forEach { parent -> parent.getInstanceMemberOrNull(name)?.let { return it } }
+        return rootObjectType.members[name]
+    }
+
+    fun getInstanceMember(atPos: Pos, name: String): ObjRecord =
+        getInstanceMemberOrNull(name)
+            ?: throw ScriptError(atPos, "symbol doesn't exist: $name")
+}
+
+

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjCollection.kt

@@ -0,0 +1,8 @@
+package net.sergeych.lyng
+
+/**
+ * Collection is an iterator with `size`]
+ */
+val ObjCollection = ObjClass("Collection", ObjIterable).apply {
+
+    }

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjInt.kt

@@ -9,6 +9,10 @@ data class ObjInt(var value: Long) : Obj(), Numeric {
 
     override fun byValueCopy(): Obj = ObjInt(value)
 
+    override fun hashCode(): Int {
+        return value.hashCode()
+    }
+
     override suspend fun getAndIncrement(context: Context): Obj {
         return ObjInt(value).also { value++ }
     }
@@ -72,7 +76,22 @@ data class ObjInt(var value: Long) : Obj(), Numeric {
         } else null
     }
 
+    override suspend fun toKotlin(context: Context): Any {
+        return value
+    }
+
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other == null || this::class != other::class) return false
+
+        other as ObjInt
+
+        return value == other.value
+    }
+
     companion object {
+        val Zero = ObjInt(0)
+        val One = ObjInt(1)
         val type = ObjClass("Int")
     }
 }

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjIterable.kt

@@ -0,0 +1,89 @@
+package net.sergeych.lyng
+
+/**
+ * Abstract class that must provide `iterator` method that returns [ObjIterator] instance.
+ */
+val ObjIterable by lazy {
+    ObjClass("Iterable").apply {
+
+        addFn("toList") {
+            val result = mutableListOf<Obj>()
+            val iterator = thisObj.invokeInstanceMethod(this, "iterator")
+
+            while (iterator.invokeInstanceMethod(this, "hasNext").toBool())
+                result += iterator.invokeInstanceMethod(this, "next")
+            ObjList(result)
+        }
+
+        // it is not effective, but it is open:
+        addFn("contains", isOpen = true) {
+            val obj = args.firstAndOnly()
+            val it = thisObj.invokeInstanceMethod(this, "iterator")
+            while (it.invokeInstanceMethod(this, "hasNext").toBool()) {
+                if (obj.compareTo(this, it.invokeInstanceMethod(this, "next")) == 0)
+                    return@addFn ObjTrue
+            }
+            ObjFalse
+        }
+
+        addFn("indexOf", isOpen = true) {
+            val obj = args.firstAndOnly()
+            var index = 0
+            val it = thisObj.invokeInstanceMethod(this, "iterator")
+            while (it.invokeInstanceMethod(this, "hasNext").toBool()) {
+                if (obj.compareTo(this, it.invokeInstanceMethod(this, "next")) == 0)
+                    return@addFn ObjInt(index.toLong())
+                index++
+            }
+            ObjInt(-1L)
+        }
+
+        addFn("toSet") {
+            val result = mutableSetOf<Obj>()
+            val it = thisObj.invokeInstanceMethod(this, "iterator")
+            while (it.invokeInstanceMethod(this, "hasNext").toBool()) {
+                result += it.invokeInstanceMethod(this, "next")
+            }
+            ObjSet(result)
+        }
+
+        addFn("toMap") {
+            val result = mutableListOf<Obj>()
+            val it = thisObj.invokeInstanceMethod(this, "iterator")
+            while (it.invokeInstanceMethod(this, "hasNext").toBool()) {
+                result += it.invokeInstanceMethod(this, "next")
+            }
+            ObjMap(ObjMap.listToMap(this, result))
+        }
+
+        addFn("forEach", isOpen = true) {
+            val it = thisObj.invokeInstanceMethod(this, "iterator")
+            val fn = requiredArg<Statement>(0)
+            while (it.invokeInstanceMethod(this, "hasNext").toBool()) {
+                val x = it.invokeInstanceMethod(this, "next")
+                fn.execute(this.copy(Arguments(listOf(x))))
+            }
+            ObjVoid
+        }
+
+        addFn("map", isOpen = true) {
+            val it = thisObj.invokeInstanceMethod(this, "iterator")
+            val fn = requiredArg<Statement>(0)
+            val result = mutableListOf<Obj>()
+            while (it.invokeInstanceMethod(this, "hasNext").toBool()) {
+                val x = it.invokeInstanceMethod(this, "next")
+                result += fn.execute(this.copy(Arguments(listOf(x))))
+            }
+            ObjList(result)
+        }
+
+        addFn("isEmpty") {
+            ObjBool(
+                thisObj.invokeInstanceMethod(this, "iterator")
+                    .invokeInstanceMethod(this, "hasNext").toBool()
+                    .not()
+            )
+        }
+
+    }
+}

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjIterator.kt

@@ -0,0 +1,3 @@
+package net.sergeych.lyng
+
+val ObjIterator by lazy { ObjClass("Iterator") }

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjKotlinIterator.kt

@@ -0,0 +1,39 @@
+@file:Suppress("unused")
+
+package net.sergeych.lyng
+
+/**
+ * Iterator wrapper to allow Kotlin collections to be returned from Lyng objects;
+ * each object is converted to a Lyng object.
+ */
+class ObjKotlinIterator(val iterator: Iterator<Any?>) : Obj() {
+
+    override val objClass = type
+
+    companion object {
+        val type = ObjClass("KotlinIterator", ObjIterator).apply {
+            addFn("next") { thisAs<ObjKotlinIterator>().iterator.next().toObj() }
+            addFn("hasNext") { thisAs<ObjKotlinIterator>().iterator.hasNext().toObj() }
+        }
+
+    }
+}
+
+/**
+ * Propagate kotlin iterator that already produces Lyng objects, no conversion
+ * is applied
+ */
+class ObjKotlinObjIterator(val iterator: Iterator<Obj>) : Obj() {
+
+    override val objClass = type
+
+    companion object {
+        val type = ObjClass("KotlinIterator", ObjIterator).apply {
+            addFn("next") {
+                thisAs<ObjKotlinObjIterator>().iterator.next()
+            }
+            addFn("hasNext") { thisAs<ObjKotlinIterator>().iterator.hasNext().toObj() }
+        }
+
+    }
+}

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjList.kt

@@ -0,0 +1,230 @@
+package net.sergeych.lyng
+
+class ObjList(val list: MutableList<Obj> = mutableListOf()) : Obj() {
+
+    init {
+        for (p in objClass.parents)
+            parentInstances.add(p.defaultInstance())
+    }
+
+    override fun toString(): String = "[${
+        list.joinToString(separator = ", ") { it.inspect() }
+    }]"
+
+    override suspend fun getAt(context: Context, index: Obj): Obj {
+        return when (index) {
+            is ObjInt -> {
+                list[index.toInt()]
+            }
+
+            is ObjRange -> {
+                when {
+                    index.start is ObjInt && index.end is ObjInt -> {
+                        if (index.isEndInclusive)
+                            ObjList(list.subList(index.start.toInt(), index.end.toInt() + 1).toMutableList())
+                        else
+                            ObjList(list.subList(index.start.toInt(), index.end.toInt()).toMutableList())
+                    }
+
+                    index.isOpenStart && !index.isOpenEnd -> {
+                        if (index.isEndInclusive)
+                            ObjList(list.subList(0, index.end!!.toInt() + 1).toMutableList())
+                        else
+                            ObjList(list.subList(0, index.end!!.toInt()).toMutableList())
+                    }
+
+                    index.isOpenEnd && !index.isOpenStart -> {
+                        ObjList(list.subList(index.start!!.toInt(), list.size).toMutableList())
+                    }
+
+                    index.isOpenStart && index.isOpenEnd -> {
+                        ObjList(list.toMutableList())
+                    }
+
+                    else -> {
+                        throw RuntimeException("Can't apply range for index: $index")
+                    }
+                }
+            }
+
+            else -> context.raiseIllegalArgument("Illegal index object for a list: ${index.inspect()}")
+        }
+    }
+
+    override suspend fun putAt(context: Context, index: Int, newValue: Obj) {
+        val i = index
+        list[i] = newValue
+    }
+
+    override suspend fun compareTo(context: Context, other: Obj): Int {
+        if (other !is ObjList) return -2
+        val mySize = list.size
+        val otherSize = other.list.size
+        val commonSize = minOf(mySize, otherSize)
+        for (i in 0..<commonSize) {
+            if (list[i].compareTo(context, other.list[i]) != 0) {
+                return list[i].compareTo(context, other.list[i])
+            }
+        }
+        // equal so far, longer is greater:
+        return when {
+            mySize < otherSize -> -1
+            mySize > otherSize -> 1
+            else -> 0
+        }
+    }
+
+    override suspend fun plus(context: Context, other: Obj): Obj =
+        when {
+            other is ObjList ->
+                ObjList((list + other.list).toMutableList())
+
+            other.isInstanceOf(ObjIterable) -> {
+                val l = other.callMethod<ObjList>(context, "toList")
+                ObjList((list + l.list).toMutableList())
+            }
+
+            else ->
+                context.raiseError("'+': can't concatenate $this with $other")
+        }
+
+
+    override suspend fun plusAssign(context: Context, other: Obj): Obj {
+        // optimization
+        if (other is ObjList) {
+            list += other.list
+            return this
+        }
+        if (other.isInstanceOf(ObjIterable)) {
+            val otherList = other.invokeInstanceMethod(context, "toList") as ObjList
+            list += otherList.list
+        } else
+            list += other
+        return this
+    }
+
+    override suspend fun contains(context: Context, other: Obj): Boolean {
+        return list.contains(other)
+    }
+
+    override val objClass: ObjClass
+        get() = type
+
+    override suspend fun toKotlin(context: Context): Any {
+        return list.map { it.toKotlin(context) }
+    }
+
+    override fun hashCode(): Int {
+        // check?
+        return list.hashCode()
+    }
+
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other == null || this::class != other::class) return false
+
+        other as ObjList
+
+        return list == other.list
+    }
+
+    companion object {
+        val type = ObjClass("List", ObjArray).apply {
+
+            createField("size",
+                statement {
+                    (thisObj as ObjList).list.size.toObj()
+                }
+            )
+            addFn("getAt") {
+                requireExactCount(1)
+                thisAs<ObjList>().getAt(this, requiredArg<Obj>(0))
+            }
+            addFn("putAt") {
+                requireExactCount(2)
+                val newValue = args[1]
+                thisAs<ObjList>().putAt(this, requiredArg<ObjInt>(0).value.toInt(), newValue)
+                newValue
+            }
+            createField("add",
+                statement {
+                    val l = thisAs<ObjList>().list
+                    for (a in args) l.add(a)
+                    ObjVoid
+                }
+            )
+            addFn("insertAt") {
+                if (args.size < 2) raiseError("addAt takes 2+ arguments")
+                val l = thisAs<ObjList>()
+                var index = requiredArg<ObjInt>(0).value.toInt()
+                for (i in 1..<args.size) l.list.add(index++, args[i])
+                ObjVoid
+            }
+
+            addFn("removeAt") {
+                val self = thisAs<ObjList>()
+                val start = requiredArg<ObjInt>(0).value.toInt()
+                if (args.size == 2) {
+                    val end = requireOnlyArg<ObjInt>().value.toInt()
+                    self.list.subList(start, end).clear()
+                } else
+                    self.list.removeAt(start)
+                self
+            }
+
+            addFn("removeLast") {
+                val self = thisAs<ObjList>()
+                if (args.isNotEmpty()) {
+                    val count = requireOnlyArg<ObjInt>().value.toInt()
+                    val size = self.list.size
+                    if (count >= size) self.list.clear()
+                    else self.list.subList(size - count, size).clear()
+                } else self.list.removeLast()
+                self
+            }
+
+            addFn("removeRange") {
+                val self = thisAs<ObjList>()
+                val list = self.list
+                val range = requiredArg<Obj>(0)
+                if (range is ObjRange) {
+                    val index = range
+                    when {
+                        index.start is ObjInt && index.end is ObjInt -> {
+                            if (index.isEndInclusive)
+                                list.subList(index.start.toInt(), index.end.toInt() + 1)
+                            else
+                                list.subList(index.start.toInt(), index.end.toInt())
+                        }
+
+                        index.isOpenStart && !index.isOpenEnd -> {
+                            if (index.isEndInclusive)
+                                list.subList(0, index.end!!.toInt() + 1)
+                            else
+                                list.subList(0, index.end!!.toInt())
+                        }
+
+                        index.isOpenEnd && !index.isOpenStart -> {
+                            list.subList(index.start!!.toInt(), list.size)
+                        }
+
+                        index.isOpenStart && index.isOpenEnd -> {
+                            list
+                        }
+
+                        else -> {
+                            throw RuntimeException("Can't apply range for index: $index")
+                        }
+                    }.clear()
+                } else {
+                    val start = range.toInt()
+                    val end = requiredArg<ObjInt>(1).value.toInt() + 1
+                    self.list.subList(start, end).clear()
+                }
+                self
+            }
+        }
+    }
+}
+
+

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjMap.kt

@@ -0,0 +1,114 @@
+package net.sergeych.lyng
+
+class ObjMapEntry(val key: Obj, val value: Obj) : Obj() {
+
+    override suspend fun compareTo(context: Context, other: Obj): Int {
+        if (other !is ObjMapEntry) return -1
+        val c = key.compareTo(context, other.key)
+        if (c != 0) return c
+        return value.compareTo(context, other.value)
+    }
+
+    override suspend fun getAt(context: Context, index: Obj): Obj = when (index.toInt()) {
+        0 -> key
+        1 -> value
+        else -> context.raiseIndexOutOfBounds()
+    }
+
+    override fun toString(): String {
+        return "$key=>$value"
+    }
+
+    override val objClass = type
+
+    companion object {
+        val type = object : ObjClass("MapEntry", ObjArray) {
+            override suspend fun callOn(context: Context): Obj {
+                return ObjMapEntry(context.requiredArg<Obj>(0), context.requiredArg<Obj>(1))
+            }
+        }.apply {
+            addFn("key") { thisAs<ObjMapEntry>().key }
+            addFn("value") { thisAs<ObjMapEntry>().value }
+            addFn("size") { 2.toObj() }
+        }
+    }
+}
+
+class ObjMap(val map: MutableMap<Obj, Obj>) : Obj() {
+
+    override val objClass = type
+
+    override suspend fun getAt(context: Context, index: Obj): Obj =
+        map.getOrElse(index) { context.raiseNoSuchElement() }
+
+    override suspend fun contains(context: Context, other: Obj): Boolean {
+        return other in map
+    }
+
+    override suspend fun compareTo(context: Context, other: Obj): Int {
+        if( other is ObjMap && other.map == map) return 0
+        return -1
+    }
+    override fun toString(): String = map.toString()
+
+    companion object {
+
+        suspend fun listToMap(context: Context, list: List<Obj>): MutableMap<Obj, Obj> {
+            val map = mutableMapOf<Obj, Obj>()
+            if (list.isEmpty()) return map
+
+            val first = list.first()
+            if (first.isInstanceOf(ObjArray)) {
+                if (first.invokeInstanceMethod(context, "size").toInt() != 2)
+                    context.raiseIllegalArgument(
+                        "list to construct map entry should exactly be 2 element Array like [key,value], got $list"
+                    )
+            } else context.raiseIllegalArgument("first element of map list be a Collection of 2 elements; got $first")
+
+
+
+            list.forEach {
+                map[it.getAt(context, ObjInt.Zero)] = it.getAt(context, ObjInt.One)
+            }
+            return map
+        }
+
+
+        val type = object : ObjClass("Map", ObjCollection) {
+            override suspend fun callOn(context: Context): Obj {
+                return ObjMap(listToMap(context, context.args.list))
+            }
+        }.apply {
+            addFn("getOrNull") {
+                val key = args.firstAndOnly(pos)
+                thisAs<ObjMap>().map.getOrElse(key) { ObjNull }
+            }
+            addFn("getOrPut") {
+                val key = requiredArg<Obj>(0)
+                thisAs<ObjMap>().map.getOrPut(key) {
+                    val lambda = requiredArg<Statement>(1)
+                    lambda.execute(this)
+                }
+            }
+            addFn("size") {
+                thisAs<ObjMap>().map.size.toObj()
+            }
+            addFn("remove") {
+                thisAs<ObjMap>().map.remove(requiredArg<Obj>(0))?.toObj() ?: ObjNull
+            }
+            addFn("clear") {
+                thisAs<ObjMap>().map.clear()
+                thisObj
+            }
+            addFn("keys") {
+                thisAs<ObjMap>().map.keys.toObj()
+            }
+            addFn("values") {
+                ObjList(thisAs<ObjMap>().map.values.toMutableList())
+            }
+            addFn("iterator") {
+                ObjKotlinIterator(thisAs<ObjMap>().map.entries.iterator())
+            }
+        }
+    }
+}

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjRange.kt

@@ -2,6 +2,9 @@ package net.sergeych.lyng
 
 class ObjRange(val start: Obj?, val end: Obj?, val isEndInclusive: Boolean) : Obj() {
 
+    val isOpenStart by lazy { start == null || start.isNull }
+    val isOpenEnd by lazy { end == null || end.isNull }
+
     override val objClass: ObjClass = type
 
     override fun toString(): String {

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjReal.kt

@@ -10,6 +10,8 @@ data class ObjReal(val value: Double) : Obj(), Numeric {
     override val toObjInt: ObjInt by lazy { ObjInt(longValue) }
     override val toObjReal: ObjReal by lazy { ObjReal(value) }
 
+    override val objClass: ObjClass = type
+
     override fun byValueCopy(): Obj = ObjReal(value)
 
     override suspend fun compareTo(context: Context, other: Obj): Int {
@@ -19,7 +21,9 @@ data class ObjReal(val value: Double) : Obj(), Numeric {
 
     override fun toString(): String = value.toString()
 
-    override val objClass: ObjClass = type
+    override fun hashCode(): Int {
+        return value.hashCode()
+    }
 
     override suspend fun plus(context: Context, other: Obj): Obj =
         ObjReal(this.value + other.toDouble())
@@ -36,6 +40,22 @@ data class ObjReal(val value: Double) : Obj(), Numeric {
     override suspend fun mod(context: Context, other: Obj): Obj =
         ObjReal(this.value % other.toDouble())
 
+    /**
+     * Returns unboxed Double value
+     */
+    override suspend fun toKotlin(context: Context): Any {
+        return value
+    }
+
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other == null || this::class != other::class) return false
+
+        other as ObjReal
+
+        return value == other.value
+    }
+
     companion object {
         val type: ObjClass = ObjClass("Real").apply {
             createField(

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjSet.kt

@@ -0,0 +1,99 @@
+package net.sergeych.lyng
+
+class ObjSet(val set: MutableSet<Obj> = mutableSetOf()) : Obj() {
+
+    override val objClass = type
+
+    override suspend fun contains(context: Context, other: Obj): Boolean {
+        return set.contains(other)
+    }
+
+    override suspend fun plus(context: Context, other: Obj): Obj {
+        return ObjSet(
+            if (other is ObjSet)
+                (set + other.set).toMutableSet()
+            else
+                (set + other).toMutableSet()
+        )
+    }
+
+    override suspend fun plusAssign(context: Context, other: Obj): Obj {
+        when (other) {
+            is ObjSet -> {
+                set += other.set
+            }
+
+            is ObjList -> {
+                set += other.list
+            }
+
+            else -> {
+                if (other.isInstanceOf(ObjIterable)) {
+                    val i = other.invokeInstanceMethod(context, "iterable")
+                    while (i.invokeInstanceMethod(context, "hasNext").toBool()) {
+                        set += i.invokeInstanceMethod(context, "next")
+                    }
+                }
+                set += other
+            }
+        }
+        return this
+    }
+
+    override suspend fun mul(context: Context, other: Obj): Obj {
+        return if (other is ObjSet) {
+            ObjSet(set.intersect(other.set).toMutableSet())
+        } else
+            context.raiseIllegalArgument("set operator * requires another set")
+    }
+
+    override suspend fun minus(context: Context, other: Obj): Obj {
+        if (other !is ObjSet)
+            context.raiseIllegalArgument("set operator - requires another set")
+        return ObjSet(set.minus(other.set).toMutableSet())
+    }
+
+    override fun toString(): String {
+        return "Set(${set.joinToString(", ")})"
+    }
+
+    override suspend fun compareTo(context: Context, other: Obj): Int {
+        return if (other !is ObjSet) -1
+        else {
+            if (set == other.set) 0
+            else -1
+        }
+    }
+
+    companion object {
+
+
+        val type = object : ObjClass("Set", ObjCollection) {
+            override suspend fun callOn(context: Context): Obj {
+                return ObjSet(context.args.list.toMutableSet())
+            }
+        }.apply {
+            addFn("size") {
+                thisAs<ObjSet>().set.size.toObj()
+            }
+            addFn("intersect") {
+                thisAs<ObjSet>().mul(this, args.firstAndOnly())
+            }
+            addFn("iterator") {
+                thisAs<ObjSet>().set.iterator().toObj()
+            }
+            addFn("union") {
+                thisAs<ObjSet>().plus(this, args.firstAndOnly())
+            }
+            addFn("subtract") {
+                thisAs<ObjSet>().minus(this, args.firstAndOnly())
+            }
+            addFn("remove") {
+                val set = thisAs<ObjSet>().set
+                val n = set.size
+                for( x in args.list ) set -= x
+                if( n == set.size ) ObjFalse else ObjTrue
+            }
+        }
+    }
+}

lynglib/src/commonMain/kotlin/net/sergeych/lyng/ObjString.kt

@@ -2,11 +2,20 @@ package net.sergeych.lyng
 
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
+import net.sergeych.sprintf.sprintf
 
 @Serializable
 @SerialName("string")
 data class ObjString(val value: String) : Obj() {
 
+//    fun normalize(context: Context, index: Int, allowsEndInclusive: Boolean = false): Int {
+//        val i = if (index < 0) value.length + index else index
+//        if (allowsEndInclusive && i == value.length) return i
+//        if (i !in value.indices) context.raiseError("index $index out of bounds for length ${value.length} of \"$value\"")
+//        return i
+//    }
+
+
     override suspend fun compareTo(context: Context, other: Obj): Int {
         if (other !is ObjString) return -2
         return this.value.compareTo(other.value)
@@ -27,8 +36,25 @@ data class ObjString(val value: String) : Obj() {
         return ObjString(value + other.asStr.value)
     }
 
-    override suspend fun getAt(context: Context, index: Int): Obj {
-        return ObjChar(value[index])
+    override suspend fun getAt(context: Context, index: Obj): Obj {
+        if( index is ObjInt ) return ObjChar(value[index.toInt()])
+        if( index is ObjRange ) {
+            val start = if(index.start == null || index.start.isNull) 0 else  index.start.toInt()
+            val end = if( index.end  == null || index.end.isNull ) value.length else  {
+                val e = index.end.toInt()
+                if( index.isEndInclusive) e + 1 else e
+            }
+            return ObjString(value.substring(start, end))
+        }
+        context.raiseIllegalArgument("String index must be Int or Range")
+    }
+
+    override fun hashCode(): Int {
+        return value.hashCode()
+    }
+
+    override suspend fun callOn(context: Context): Obj {
+        return ObjString(this.value.sprintf(*context.args.toKotlinList(context).toTypedArray()))
     }
 
     override suspend fun contains(context: Context, other: Obj): Boolean {
@@ -36,15 +62,26 @@ data class ObjString(val value: String) : Obj() {
             value.contains(other.value)
         else if (other is ObjChar)
             value.contains(other.value)
-        else context.raiseArgumentError("String.contains can't take $other")
+        else context.raiseIllegalArgument("String.contains can't take $other")
+    }
+
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other == null || this::class != other::class) return false
+
+        other as ObjString
+
+        return value == other.value
     }
 
     companion object {
         val type = ObjClass("String").apply {
-            addConst("startsWith",
-                statement {
-                    ObjBool(thisAs<ObjString>().value.startsWith(requiredArg<ObjString>(0).value))
-                })
+            addFn("startsWith") {
+                ObjBool(thisAs<ObjString>().value.startsWith(requiredArg<ObjString>(0).value))
+            }
+            addFn("endsWith") {
+                ObjBool(thisAs<ObjString>().value.endsWith(requiredArg<ObjString>(0).value))
+            }
             addConst("length",
                 statement { ObjInt(thisAs<ObjString>().value.length.toLong()) }
             )

lynglib/src/commonMain/kotlin/net/sergeych/lyng/Parser.kt

@@ -45,12 +45,18 @@ private class Parser(fromPos: Pos) {
             '=' -> {
                 if (pos.currentChar == '=') {
                     pos.advance()
-                    if (currentChar == '=') {
-                        pos.advance()
-                        Token("===", from, Token.Type.REF_EQ)
-                    } else
-                        Token("==", from, Token.Type.EQ)
-                } else
+                    when (currentChar) {
+                        '=' -> {
+                            pos.advance()
+                            Token("===", from, Token.Type.REF_EQ)
+                        }
+                        else -> Token("==", from, Token.Type.EQ)
+                    }
+                } else if( currentChar == '>' ) {
+                    pos.advance()
+                    Token("=>", from, Token.Type.EQARROW)
+                }
+                else
                     Token("=", from, Token.Type.ASSIGN)
             }
 
@@ -142,10 +148,12 @@ private class Parser(fromPos: Pos) {
                             pos.advance()
                             Token("...", from, Token.Type.ELLIPSIS)
                         }
+
                         '<' -> {
                             pos.advance()
                             Token("..<", from, Token.Type.DOTDOTLT)
                         }
+
                         else -> {
                             Token("..", from, Token.Type.DOTDOT)
                         }
@@ -157,11 +165,10 @@ private class Parser(fromPos: Pos) {
             '<' -> {
                 if (currentChar == '=') {
                     pos.advance()
-                    if( currentChar == '>' ) {
+                    if (currentChar == '>') {
                         pos.advance()
                         Token("<=>", from, Token.Type.SHUTTLE)
-                    }
-                    else {
+                    } else {
                         Token("<=", from, Token.Type.LTE)
                     }
                 } else
@@ -240,6 +247,7 @@ private class Parser(fromPos: Pos) {
             }
 
             '"' -> loadStringToken()
+
             in digitsSet -> {
                 pos.back()
                 decodeNumber(loadChars(digits), from)
@@ -265,6 +273,21 @@ private class Parser(fromPos: Pos) {
                 Token(value.toString(), start, Token.Type.CHAR)
             }
 
+            '?' -> {
+                when(currentChar.also { pos.advance() }) {
+                    ':' -> Token("??", from, Token.Type.ELVIS)
+                    '?' -> Token("??", from, Token.Type.ELVIS)
+                    '.' -> Token("?.", from, Token.Type.NULL_COALESCE)
+                    '[' -> Token("?(", from, Token.Type.NULL_COALESCE_INDEX)
+                    '(' -> Token("?(", from, Token.Type.NULL_COALESCE_INVOKE)
+                    '{' -> Token("?{", from, Token.Type.NULL_COALESCE_BLOCKINVOKE)
+                    else -> {
+                        pos.back()
+                        Token("?", from, Token.Type.QUESTION)
+                    }
+                }
+            }
+
             else -> {
                 // text infix operators:
                 // Labels processing is complicated!
@@ -295,7 +318,7 @@ private class Parser(fromPos: Pos) {
     private fun decodeNumber(p1: String, start: Pos): Token =
         if (pos.end)
             Token(p1, start, Token.Type.INT)
-        else if( currentChar == 'e' || currentChar == 'E' ) {
+        else if (currentChar == 'e' || currentChar == 'E') {
             pos.advance()
             var negative = false
             if (currentChar == '+')
@@ -353,10 +376,11 @@ private class Parser(fromPos: Pos) {
     private val currentChar: Char get() = pos.currentChar
 
     private fun loadStringToken(): Token {
-        var start = currentPos
+        val start = currentPos
 
-        if (currentChar == '"') pos.advance()
-        else start = start.back()
+//        if (currentChar == '"') pos.advance()
+//        else start = start.back()
+//        start = start.back()
 
         val sb = StringBuilder()
         while (currentChar != '"') {

lynglib/src/commonMain/kotlin/net/sergeych/lyng/Pos.kt

@@ -5,6 +5,7 @@ data class Pos(val source: Source, val line: Int, val column: Int) {
         return "${source.fileName}:${line+1}:${column}"
     }
 
+    @Suppress("unused")
     fun back(): Pos =
         if( column > 0) Pos(source, line, column-1)
         else if( line > 0) Pos(source, line-1, source.lines[line-1].length - 1)

lynglib/src/commonMain/kotlin/net/sergeych/lyng/Script.kt

@@ -146,26 +146,32 @@ class Script(
                 delay((this.args.firstAndOnly().toDouble()/1000.0).roundToLong())
             }
 
+            addConst("Object", rootObjectType)
             addConst("Real", ObjReal.type)
             addConst("String", ObjString.type)
             addConst("Int", ObjInt.type)
             addConst("Bool", ObjBool.type)
             addConst("Char", ObjChar.type)
             addConst("List", ObjList.type)
+            addConst("Set", ObjSet.type)
             addConst("Range", ObjRange.type)
+            addConst("Map", ObjMap.type)
+            addConst("MapEntry", ObjMapEntry.type)
             @Suppress("RemoveRedundantQualifierName")
             addConst("Callable", Statement.type)
             // interfaces
             addConst("Iterable", ObjIterable)
+            addConst("Collection", ObjCollection)
             addConst("Array", ObjArray)
             addConst("Class", ObjClassType)
-            addConst("Object", Obj().objClass)
 
             val pi = ObjReal(PI)
             addConst("π", pi)
             getOrCreateNamespace("Math").apply {
                 addConst("PI", pi)
             }
+
+
         }
     }
 }

lynglib/src/commonMain/kotlin/net/sergeych/lyng/Token.kt

@@ -14,13 +14,18 @@ data class Token(val value: String, val pos: Pos, val type: Type) {
         IN, NOTIN, IS, NOTIS,
         EQ, NEQ, LT, LTE, GT, GTE, REF_EQ, REF_NEQ,
         SHUTTLE,
-        AND, BITAND, OR, BITOR, NOT, BITNOT, DOT, ARROW, QUESTION, COLONCOLON,
+        AND, BITAND, OR, BITOR, NOT, BITNOT, DOT, ARROW, EQARROW, QUESTION, COLONCOLON,
         SINLGE_LINE_COMMENT, MULTILINE_COMMENT,
         LABEL, ATLABEL, // label@ at@label
         //PUBLIC, PROTECTED, INTERNAL, EXPORT, OPEN, INLINE, OVERRIDE, ABSTRACT, SEALED, EXTERNAL, VAL, VAR, CONST, TYPE, FUN, CLASS, INTERFACE, ENUM, OBJECT, TRAIT, THIS,
         ELLIPSIS, DOTDOT, DOTDOTLT,
         NEWLINE,
         EOF,
+        NULL_COALESCE,
+        ELVIS,
+        NULL_COALESCE_INDEX,
+        NULL_COALESCE_INVOKE,
+        NULL_COALESCE_BLOCKINVOKE,
     }
 
     companion object {

lynglib/src/commonMain/kotlin/net/sergeych/lyng/TypeDecl.kt

@@ -0,0 +1,14 @@
+@file:Suppress("unused")
+
+package net.sergeych.lyng
+
+// this is highly experimental and subject to complete redesign
+// very soon
+sealed class TypeDecl(val isNullable:Boolean = false) {
+    // ??
+//    data class Fn(val argTypes: List<ArgsDeclaration.Item>, val retType: TypeDecl) : TypeDecl()
+    object TypeAny : TypeDecl()
+    object TypeNullableAny : TypeDecl(true)
+
+    class Simple(val name: String,isNullable: Boolean) : TypeDecl(isNullable)
+}

lynglib/src/commonTest/kotlin/ScriptTest.kt

@@ -1,4 +1,3 @@
-package io.github.kotlin.fibonacci
 
 import kotlinx.coroutines.test.runTest
 import net.sergeych.lyng.*
@@ -111,25 +110,25 @@ class ScriptTest {
         assertEquals(Token("label", src.posAt(0, 12), Token.Type.ATLABEL), tt[2])
     }
 
-    @Test
-    fun parse0Test() {
-        val src = """
-            println("Hello")
-            println( "world" )
-        """.trimIndent().toSource()
-
-        val p = parseLyng(src).listIterator()
-
-        assertEquals(Token("println", src.posAt(0, 0), Token.Type.ID), p.next())
-        assertEquals(Token("(", src.posAt(0, 7), Token.Type.LPAREN), p.next())
-        assertEquals(Token("Hello", src.posAt(0, 8), Token.Type.STRING), p.next())
-        assertEquals(Token(")", src.posAt(0, 15), Token.Type.RPAREN), p.next())
-        assertEquals(Token("\n", src.posAt(0, 16), Token.Type.NEWLINE), p.next())
-        assertEquals(Token("println", src.posAt(1, 0), Token.Type.ID), p.next())
-        assertEquals(Token("(", src.posAt(1, 7), Token.Type.LPAREN), p.next())
-        assertEquals(Token("world", src.posAt(1, 9), Token.Type.STRING), p.next())
-        assertEquals(Token(")", src.posAt(1, 17), Token.Type.RPAREN), p.next())
-    }
+//    @Test
+//    fun parse0Test() {
+//        val src = """
+//            println("Hello")
+//            println( "world" )
+//        """.trimIndent().toSource()
+//
+//        val p = parseLyng(src).listIterator()
+//
+//        assertEquals(Token("println", src.posAt(0, 0), Token.Type.ID), p.next())
+//        assertEquals(Token("(", src.posAt(0, 7), Token.Type.LPAREN), p.next())
+//        assertEquals(Token("Hello", src.posAt(0, 9), Token.Type.STRING), p.next())
+//        assertEquals(Token(")", src.posAt(0, 15), Token.Type.RPAREN), p.next())
+//        assertEquals(Token("\n", src.posAt(0, 16), Token.Type.NEWLINE), p.next())
+//        assertEquals(Token("println", src.posAt(1, 0), Token.Type.ID), p.next())
+//        assertEquals(Token("(", src.posAt(1, 7), Token.Type.LPAREN), p.next())
+//        assertEquals(Token("world", src.posAt(1, 9), Token.Type.STRING), p.next())
+//        assertEquals(Token(")", src.posAt(1, 17), Token.Type.RPAREN), p.next())
+//    }
 
     @Test
     fun parse1Test() {
@@ -1056,7 +1055,7 @@ class ScriptTest {
     }
 
     @Test
-    fun testIntOpenRangeInclusive() = runTest {
+    fun testIntClosedRangeInclusive() = runTest {
         eval(
             """
             val r = 10 .. 20
@@ -1090,7 +1089,7 @@ class ScriptTest {
     }
 
     @Test
-    fun testIntOpenRangeExclusive() = runTest {
+    fun testIntClosedRangeExclusive() = runTest {
         eval(
             """
             val r = 10 ..< 20
@@ -1126,7 +1125,7 @@ class ScriptTest {
     }
 
     @Test
-    fun testIntOpenRangeInExclusive() = runTest {
+    fun testIntClosedRangeInExclusive() = runTest {
         eval(
             """
                 assert( (1..3) !in (1..<3) )
@@ -1135,6 +1134,43 @@ class ScriptTest {
         )
     }
 
+    @Test
+    fun testOpenStartRanges() = runTest {
+        eval(
+            """
+            var r = ..5
+            assert( r::class == Range)
+            assert( r.start == null)
+            assert( r.end == 5)
+            assert( r.isEndInclusive)
+            
+            r = ..< 5
+            assert( r::class == Range)
+            assert( r.start == null)
+            assert( r.end == 5)
+            assert( !r.isEndInclusive)
+            
+            assert( r.start == null)
+            
+            assert( (-2..3) in r)
+            assert( (-2..12) !in r)
+            
+        """.trimIndent()
+        )
+    }
+
+    @Test
+    fun testOpenEndRanges() = runTest {
+        eval(
+            """
+            var r = 5..
+            assert( r::class == Range)
+            assert( r.end == null)
+            assert( r.start == 5)
+        """.trimIndent()
+        )
+    }
+
     @Test
     fun testCharacterRange() = runTest {
         eval(
@@ -1184,21 +1220,6 @@ class ScriptTest {
         println(a)
     }
 
-    @Test
-    fun iterableList() = runTest {
-        // 473
-        eval(
-            """
-            for( i in 0..<1024 ) {    
-            val list = (1..1024).toList()
-            assert(list.size == 1024)
-            assert(list[0] == 1)
-            assert(list[-1] == 1024)
-            }
-        """.trimIndent()
-        )
-    }
-
     @Test
     fun testLambdaWithIt1() = runTest {
         eval(
@@ -1245,7 +1266,12 @@ class ScriptTest {
         eval(
             """
             val x = { x, y, z ->
+                println("-- x=",x)
+                println("-- y=",y)
+                println("-- z=",z)
+                println([x,y,z])
                 assert( [x, y, z] == [1,2,"end"])
+                println("----:")
             }
             assert( x(1, 2, "end") == void)
         """.trimIndent()
@@ -1868,7 +1894,7 @@ class ScriptTest {
     fun testThrowFromKotlin() = runTest {
         val c = Context()
         c.addFn("callThrow") {
-            raiseArgumentError("fromKotlin")
+            raiseIllegalArgument("fromKotlin")
         }
         c.eval(
             """
@@ -2113,4 +2139,149 @@ class ScriptTest {
     """.trimIndent()
         )
     }
+
+    @Test
+    fun testNull1() = runTest {
+        eval(
+            """
+            var s = null
+            assertThrows { s.length }
+            assertThrows { s.size() }
+            
+            assertEquals( null, s?.size() )
+            assertEquals( null, s?.length )
+            assertEquals( null, s?.length ?{ "test" } )
+            assertEquals( null, s?[1] )
+            assertEquals( null, s ?{ "test" } )
+            
+            s = "xx"
+            assert(s.lower().size == 2)
+            assert(s.length == 2)
+        """.trimIndent()
+        )
+    }
+
+    @Test
+    fun testSprintf() = runTest {
+        eval(
+            """ 
+            assertEquals( "123.45", "%3.2f"(123.451678) )
+            assertEquals( "123.45: hello", "%3.2f: %s"(123.451678, "hello") )
+            assertEquals( "123.45: true", "%3.2f: %s"(123.451678, true) )
+        """.trimIndent()
+        )
+    }
+
+    @Test
+    fun testSubstringRangeFailure() = runTest {
+        eval(
+            """ 
+            assertEquals("pult", "catapult"[4..])
+            assertEquals("cat", "catapult"[..2])
+            """.trimIndent()
+        )
+    }
+
+    @Test
+    fun passingOpenEndedRangeAsParam() = runTest {
+        eval(
+            """
+                fun test(r) {
+                    assert( r is Range ) 
+                }
+                test( 1.. )
+            """.trimIndent()
+        )
+    }
+
+    @Test
+    fun testCollectionStructure() = runTest {
+        eval(
+            """
+                val list = [1,2,3]
+                assert( 1 in list )
+                assert( list.indexOf(3) == 2 )
+                assert( list.indexOf(5) == -1 )
+                assert( list is List )
+                assert( list is Array )
+                assert( list is Iterable )
+                assert( list is Collection )
+                
+                val other = []
+                list.forEach { other += it }
+                assertEquals( list, other )
+                
+                assert( list.isEmpty() == false )
+                
+                assertEquals( [10, 20, 30], list.map { it * 10 } )
+                assertEquals( [10, 20, 30], (1..3).map { it * 10 } )
+                
+            """.trimIndent()
+        )
+    }
+
+    @Test
+    fun testSet() = runTest {
+        eval(
+            """
+            val set = Set(1,2,3)
+            
+            assert( set.contains(1) )
+            assert( 1 in set )
+            
+            assert(set is Set)
+            assert(set is Iterable)
+            assert(set is Collection)
+            println(set)
+            for( x in set ) println(x)
+            assert([1,2,3] == set.toList())
+            set += 4
+            assert(set.toList() == [1,2,3,4])
+            assert(set == Set(1,2,3,4))
+            
+            val s1 = [1, 2].toSet()
+            assertEquals( Set(1,2), s1 * set) 
+            
+        """.trimIndent()
+        )
+    }
+
+    @Test
+    fun testLet() = runTest {
+        eval("""
+            class Point(x=0,y=0)
+            assert( Point() is Object) 
+            Point().let { println(it.x, it.y) }
+            val x = null
+            x?.let { println(it.x, it.y) }
+        """.trimIndent())
+    }
+
+    @Test
+    fun testApply() = runTest {
+        eval("""
+            class Point(x,y)
+            // see the difference: apply changes this to newly created Point:
+            val p = Point(1,2).apply { 
+                x++; y++ 
+            }
+            assertEquals(p, Point(2,3))
+            >>> void
+
+        """.trimIndent())
+    }
+
+    @Test
+    fun testApplyThis() = runTest {
+        eval("""
+            class Point(x,y)
+            // see the difference: apply changes this to newly created Point:
+            val p = Point(1,2).apply { 
+                this.x++; this.y++ 
+            }
+            assertEquals(p, Point(2,3))
+            >>> void
+
+        """.trimIndent())
+    }
 }

lynglib/src/commonTest/kotlin/TypesTest.kt

@@ -0,0 +1,53 @@
+import kotlinx.coroutines.test.runTest
+import net.sergeych.lyng.eval
+import kotlin.test.Test
+
+class TypesTest {
+
+    @Test
+    fun testTypeCollection1() = runTest {
+        eval("""
+           class Point(x: Real, y: Real)
+           assert(Point(1,2).x == 1)
+           assert(Point(1,2).y == 2)
+           assert(Point(1,2) is Point)
+        """.trimIndent())
+
+    }
+    @Test
+    fun testTypeCollection2() = runTest {
+        eval("""
+           fun fn1(x: Real, y: Real): Real { x + y }
+        """.trimIndent())
+
+    }
+    @Test
+    fun testTypeCollection3() = runTest {
+        eval("""
+           class Test(a: Int) {
+              fun fn1(x: Real, y: Real): Real { x + y }
+           }
+        """.trimIndent())
+    }
+
+    @Test
+    fun testExternDeclarations() = runTest {
+        eval("""
+            extern fun foo1(a: String): Void
+            assertThrows { foo1("1") }
+           class Test(a: Int) {
+              extern fun fn1(x: Real, y: Real): Real
+//              extern val b: Int
+           }
+//           println("1")
+           val t = Test(0)
+//           println(t.b)
+//           println("2")
+           assertThrows {
+            t.fn1(1,2)
+           }
+//           println("4")
+           
+        """.trimIndent())
+    }
+}

lynglib/src/jvmTest/kotlin/BookTest.kt

@@ -255,6 +255,16 @@ class BookTest {
         runDocTests("../docs/Range.md")
     }
 
+    @Test
+    fun testSet() = runTest {
+        runDocTests("../docs/Set.md")
+    }
+
+    @Test
+    fun testMap() = runTest {
+        runDocTests("../docs/Map.md")
+    }
+
     @Test
     fun testSampleBooks() = runTest {
         for (bt in Files.list(Paths.get("../docs/samples")).toList()) {

settings.gradle.kts

@@ -18,5 +18,5 @@ dependencyResolutionManagement {
 }
 
 rootProject.name = "lyng"
-include(":library")
+include(":lynglib")
 include(":lyng")