Lyng: modern scripting for kotlin multiplatform

A KMP library and a standalone interpreter

• simple, compact, intuitive and elegant modern code:

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 (JVM, JS, WasmJS, Lunux, MacOS, iOS, Windows)
• 100% secure: no access to any API you didn't explicitly provide
• 100% coroutines! Every function/script is a coroutine, it does not block the thread, no async/await/suspend keyword garbage, see parallelism

  val deferred = launch {
    delay(1.5) // coroutine is delayed for 1.5s, thread is not blocked!
    "done"
  }
  // ...
  // suspend current coroutine, no thread is blocked again,
  // and wait for deferred to return something:
  assertEquals("donw", deferred.await())

and it is multithreaded on platforms supporting it (automatically, no code changes required, just launch more coroutines and they will be executed concurrently if possible). See parallelism

• functional style and OOP together, multiple inheritance, implementing interfaces for existing classes, writing extensions.
• Any Unicode letters can be used as identifiers: assert( sin(π/2) == 1 ).

Resources:

• introduction and tutorial - start here please
• Samples directory
• Books directory

Integration in Kotlin multiplatform

Add dependency to your project

// 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:

comminMain by getting {
    dependencies {
        // ...
        implementation("net.sergeych:lynglib:$lyngVersion")
    }
}

Now you can import lyng and use it:

Execute script:

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

Script is executed over some Scope. Create instance, add your specific vars and functions to it, and call:

import com.sun.source.tree.Scope
import new.sergeych.lyng.*

// simple function
val scope = Script.newScope().apply {
    addFn("sumOf") {
        var sum = 0.0
        for (a in args) sum += a.toDouble()
        ObjReal(sum)
    }
    addConst("LIGHT_SPEED", ObjReal(299_792_458.0))

    // callback back to kotlin to some suspend fn, for example::
    // suspend fun doSomeWork(text: String): Int
    addFn("doSomeWork") {
        // this _is_ a suspend lambda, we can call suspend function,
        // and it won't consume the thread.
        // note that in kotlin handler, `args` is a list of `Obj` arguments
        // and return value from this lambda should be Obj too:
        doSomeWork(args[0]).toObj()
    }
}
// adding constant:
scope.eval("sumOf(1,2,3)") // <- 6

Note that the scope stores all changes in it so you can make calls on a single scope to preserve state between calls.

Why?

Designed to add scripting to kotlin multiplatform application in easy and efficient way. This is attempt to achieve what Lua is for C/++.

• fast start (times and times faster than initializing v8/wasm)
• fast and simple kotlin interoperability
• coroutine-based, truly async. On platforms with multithreading, run multithreaded. No python/ruby/javascript threads hell.
• small footprint
• absolutely safe: no access to any dangerous or sensitive functions until you specifically provide it.

Language

• Javascript, WasmJS, native, JVM, android - batteries included.
• dynamic types in most elegant and concise way
• async, 100% coroutines, supports multiple cores where platform supports thread
• good for functional an object-oriented style

Language Roadmap

v1.0.0

Planned autumn 2025. Complete dynamic language with sufficient standard library:

Ready features:

• Language platform and independent command-line launcher

• Integral types and user classes, variables and constants, functions

• lambdas and closures, coroutines for all callables

• while-else, do-while-else, for-else loops with break-continue returning values and labels support

• ranges, lists, strings, interfaces: Iterable, Iterator, Collection, Array

• when(value), if-then-else

• exception handling: throw, try-catch-finally, exception classes.

• multiplatform maven publication

• documentation for the current state

• maps, sets and sequences (flows?)

• modules

• string formatting and tools

• launch, deferred, CompletableDeferred, Mutex, etc.

• multiline strings

• typesafe bit-effective serialization

• compression/decompression (integrated in serialization)

• Under way:

• regular exceptions

• multiple inheritance for user classes

• 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
• metadata first class access from lyng

Further

• client with GUI support based on compose multiplatform somehow
• notebook - style workbooks with graphs, formulae, etc.
• language server or compose-based lyng-aware editor