OO: added inheritance, Collection, Iterator, Iterable, Array. Range is rewritten to be Iterable. Math namespace is temporarily broken (to be updated to new ObjClass model).

docs/Iterable.md

@@ -0,0 +1,31 @@
+# Iterable interface
+
+The inteface which requires iterator to be implemented:
+
+    fun iterator(): Iterator
+
+Iterator itself is a simple interface that should provide only to method:
+
+    interface Iterable {
+        fun hasNext(): Bool
+        fun next(): Obj
+    }
+
+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:
+
+## 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]
+
+## Implemented in classes:
+
+- [List], [Range]
+
+[List]: List.md
+[Range]: Range.md

docs/Range.md

@@ -45,27 +45,12 @@ are equal or within another, taking into account the end-inclusiveness:
     assert( (1..<3) in (1..3) )
     >>> void
 
-## Range size and indexed access
+## Finite Ranges are iterable
 
-This might be confusing, but the range size and limits are used with for loops
-so their meaning is special.
+So given a range with both ends, you can assume it is [Iterable]. This automatically let
+use finite ranges in loops and convert it to lists:
 
-For open ranges, size throws and exception.
-For Int ranges, the `size` is `end` - `start` possibly + 1 for ind-inclusive ranges, and indexing getter returns all values from start to end, probably, inclusive:
-
-    val r = 1..3
-    assert( r.size == 3 )
-    assert( r[0] == 1 )
-    assert( r[1] == 2 )
-    assert( r[2] == 3 )
-    >>> void
-
-And for end-exclusive range:
-
-    val r = 1..<3
-    assert(r.size == 2)
-    assert( r[0] == 1 )
-    assert( r[1] == 2 )
+    assert( [-2, -1, 0, 1] == (-2..1).toList() )
     >>> void
 
 In spite of this you can use ranges in for loops:
@@ -102,8 +87,8 @@ You can use Char as both ends of the closed range:
 
 Exclusive end char ranges are supported too:
 
-    ('a'..<'c').size
-    >>> 2
+    ('a'..<'c').toList 
+    >>> ['a', 'b']
 
 
 # Instance members
@@ -119,3 +104,5 @@ Exclusive end char ranges are supported too:
 | size            | for finite ranges, see above | Long          |
 | []              | see above                    |               |
 |                 |                              |               |
+
+[Iterable]: Iterable.md

library/build.gradle.kts

@@ -49,6 +49,7 @@ kotlin {
                 //put your multiplatform dependencies here
                 implementation(libs.kotlinx.coroutines.core)
                 implementation(libs.mp.bintools)
+                implementation("net.sergeych:mp_stools:1.5.2")
             }
         }
         val commonTest by getting {

library/src/commonMain/kotlin/net/sergeych/ling/Compiler.kt

@@ -144,7 +144,7 @@ class Compiler(
                                     context.pos = next.pos
                                     val v = left.getter(context).value
                                     WithAccess(
-                                        v.callInstanceMethod(
+                                        v.invokeInstanceMethod(
                                             context,
                                             next.value,
                                             args.toArguments(context)
@@ -540,43 +540,50 @@ class Compiler(
 
                 // insofar we suggest source object is enumerable. Later we might need to add checks
                 val sourceObj = source.execute(forContext)
-                val size = runCatching { sourceObj.callInstanceMethod(forContext, "size").toInt() }
-                    .getOrElse { throw ScriptError(tOp.pos, "object is not enumerable: no size", it) }
-                var result: Obj = ObjVoid
-                var breakCaught = false
-                if (size > 0) {
-                    var current = runCatching { sourceObj.getAt(forContext, 0) }
-                        .getOrElse {
-                            throw ScriptError(
-                                tOp.pos,
-                                "object is not enumerable: no index access for ${sourceObj.inspect()}",
-                                it
-                            )
+
+                if (sourceObj.isInstanceOf(ObjIterable)) {
+                    loopIterable(forContext, sourceObj, loopSO, body, elseStatement, label)
+                } else {
+                    val size = runCatching { sourceObj.invokeInstanceMethod(forContext, "size").toInt() }
+                        .getOrElse { throw ScriptError(tOp.pos, "object is not enumerable: no size", it) }
+
+                    var result: Obj = ObjVoid
+                    var breakCaught = false
+
+                    if (size > 0) {
+                        var current = runCatching { sourceObj.getAt(forContext, 0) }
+                            .getOrElse {
+                                throw ScriptError(
+                                    tOp.pos,
+                                    "object is not enumerable: no index access for ${sourceObj.inspect()}",
+                                    it
+                                )
+                            }
+                        var index = 0
+                        while (true) {
+                            loopSO.value = current
+                            try {
+                                result = body.execute(forContext)
+                            } catch (lbe: LoopBreakContinueException) {
+                                if (lbe.label == label || lbe.label == null) {
+                                    breakCaught = true
+                                    if (lbe.doContinue) continue
+                                    else {
+                                        result = lbe.result
+                                        break
+                                    }
+                                } else
+                                    throw lbe
+                            }
+                            if (++index >= size) break
+                            current = sourceObj.getAt(forContext, index)
                         }
-                    var index = 0
-                    while (true) {
-                        loopSO.value = current
-                        try {
-                            result = body.execute(forContext)
-                        } catch (lbe: LoopBreakContinueException) {
-                            if (lbe.label == label || lbe.label == null) {
-                                breakCaught = true
-                                if (lbe.doContinue) continue
-                                else {
-                                    result = lbe.result
-                                    break
-                                }
-                            } else
-                                throw lbe
-                        }
-                        if (++index >= size) break
-                        current = sourceObj.getAt(forContext, index)
                     }
+                    if (!breakCaught && elseStatement != null) {
+                        result = elseStatement.execute(it)
+                    }
+                    result
                 }
-                if (!breakCaught && elseStatement != null) {
-                    result = elseStatement.execute(it)
-                }
-                result
             }
         } else {
             // maybe other loops?
@@ -584,10 +591,31 @@ class Compiler(
         }
     }
 
+    private suspend fun loopIterable(
+        forContext: Context, sourceObj: Obj, loopVar: StoredObj,
+        body: Statement, elseStatement: Statement?, label: String?
+    ): Obj {
+        val iterObj = sourceObj.invokeInstanceMethod(forContext, "iterator")
+        var result: Obj = ObjVoid
+        while (iterObj.invokeInstanceMethod(forContext, "hasNext").toBool()) {
+            try {
+                loopVar.value = iterObj.invokeInstanceMethod(forContext, "next")
+                result = body.execute(forContext)
+            } catch (lbe: LoopBreakContinueException) {
+                if (lbe.label == label || lbe.label == null) {
+                    if (lbe.doContinue) continue
+                }
+                return lbe.result
+            }
+        }
+        return elseStatement?.execute(forContext) ?: result
+    }
+
     private fun parseWhileStatement(cc: CompilerContext): Statement {
         val label = getLabel(cc)?.also { cc.labels += it }
         val start = ensureLparen(cc)
-        val condition = parseExpression(cc) ?: throw ScriptError(start, "Bad while statement: expected expression")
+        val condition =
+            parseExpression(cc) ?: throw ScriptError(start, "Bad while statement: expected expression")
         ensureRparen(cc)
 
         val body = parseStatement(cc) ?: throw ScriptError(start, "Bad while statement: expected statement")
@@ -958,6 +986,8 @@ class Compiler(
             // in, is:
             Operator.simple(Token.Type.IN, lastPrty) { c, a, b -> ObjBool(b.contains(c, a)) },
             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)) },
             // shuttle <=> 6
             // bit shifts 7
             Operator.simple(Token.Type.PLUS, ++lastPrty) { ctx, a, b -> a.plus(ctx, b) },

library/src/commonMain/kotlin/net/sergeych/ling/Obj.kt

@@ -4,6 +4,7 @@ import kotlinx.coroutines.sync.Mutex
 import kotlinx.coroutines.sync.withLock
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
+import net.sergeych.synctools.ProtectedOp
 
 //typealias InstanceMethod = (Context, Obj) -> Obj
 
@@ -18,16 +19,15 @@ data class Accessor(
     fun setter(pos: Pos) = setterOrNull ?: throw ScriptError(pos, "can't assign value")
 }
 
-sealed class Obj {
+open class Obj {
     var isFrozen: Boolean = false
 
     private val monitor = Mutex()
 
-    // members: fields most often
-    private val members = mutableMapOf<String, WithAccess<Obj>>()
-
     //    private val memberMutex = Mutex()
-    private val parentInstances = listOf<Obj>()
+    internal var parentInstances: MutableList<Obj> = mutableListOf()
+
+    private val opInstances = ProtectedOp()
 
     open fun inspect(): String = toString()
 
@@ -39,20 +39,12 @@ sealed class Obj {
      */
     open fun byValueCopy(): Obj = this
 
-    /**
-     * Get instance member traversing the hierarchy if needed. Its meaning is different for different objects.
-     */
-    fun getInstanceMemberOrNull(name: String): WithAccess<Obj>? {
-        members[name]?.let { return it }
-        parentInstances.forEach { parent -> parent.getInstanceMemberOrNull(name)?.let { return it } }
-        return null
-    }
+    fun isInstanceOf(someClass: Obj) = someClass === objClass || objClass.allParentsSet.contains(someClass)
 
-    fun getInstanceMember(atPos: Pos, name: String): WithAccess<Obj> =
-        getInstanceMemberOrNull(name)
-            ?: throw ScriptError(atPos, "symbol doesn't exist: $name")
+    suspend fun invokeInstanceMethod(context: Context, name: String, vararg args: Obj): Obj =
+        invokeInstanceMethod(context, name, Arguments(args.map { Arguments.Info(it, context.pos) }))
 
-    suspend fun callInstanceMethod(
+    suspend fun invokeInstanceMethod(
         context: Context,
         name: String,
         args: Arguments = Arguments.EMPTY
@@ -60,6 +52,8 @@ sealed class Obj {
         // note that getInstanceMember traverses the hierarchy
         objClass.getInstanceMember(context.pos, name).value.invoke(context, this, args)
 
+    fun getMemberOrNull(name: String): Obj? = objClass.getInstanceMemberOrNull(name)?.value
+
     // methods that to override
 
     open suspend fun compareTo(context: Context, other: Obj): Int {
@@ -170,14 +164,15 @@ sealed class Obj {
                 value.execute(context.copy(context.pos, newThisObj = this)).asReadonly
             }
             // could be writable property naturally
-            else -> getInstanceMember(context.pos, name)
+            null -> ObjNull.asReadonly
+            else -> obj
         }
     }
 
     fun writeField(context: Context, name: String, newValue: Obj) {
         willMutate(context)
-        members[name]?.let { if (it.isMutable) it.value = newValue }
-            ?: context.raiseError("Can't reassign member: $name")
+        val field = objClass.getInstanceMemberOrNull(name) ?: context.raiseError("no such field: $name")
+        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 {
@@ -188,18 +183,6 @@ sealed class Obj {
         context.raiseNotImplemented("indexing")
     }
 
-    fun createField(name: String, initialValue: Obj, isMutable: Boolean = false, pos: Pos = Pos.builtIn) {
-        if (name in members || parentInstances.any { name in it.members })
-            throw ScriptError(pos, "$name is already defined in $objClass or one of its supertypes")
-        members[name] = WithAccess(initialValue, isMutable)
-    }
-
-    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)
-
     open suspend fun callOn(context: Context): Obj {
         context.raiseNotImplemented()
     }
@@ -207,6 +190,24 @@ sealed class Obj {
     suspend fun invoke(context: Context, thisObj: Obj, args: Arguments): Obj =
         callOn(context.copy(context.pos, args = args, newThisObj = thisObj))
 
+    suspend fun invoke(context: Context, thisObj: Obj, vararg args: Obj): Obj =
+        callOn(
+            context.copy(
+                context.pos,
+                args = Arguments(args.map { Arguments.Info(it, context.pos) }),
+                newThisObj = thisObj
+            )
+        )
+
+    suspend fun invoke(context: Context, thisObj: Obj): Obj =
+        callOn(
+            context.copy(
+                context.pos,
+                args = Arguments.EMPTY,
+                newThisObj = thisObj
+            )
+        )
+
     suspend fun invoke(context: Context, atPos: Pos, thisObj: Obj, args: Arguments): Obj =
         callOn(context.copy(atPos, args = args, newThisObj = thisObj))
 
@@ -277,7 +278,7 @@ fun Obj.toDouble(): Double =
 
 @Suppress("unused")
 fun Obj.toLong(): Long =
-    when(this) {
+    when (this) {
         is Numeric -> longValue
         is ObjString -> value.toLong()
         is ObjChar -> value.code.toLong()
@@ -305,4 +306,6 @@ class ObjNullPointerError(context: Context) : ObjError(context, "object is null"
 class ObjAssertionError(context: Context, message: String) : ObjError(context, message)
 class ObjClassCastError(context: Context, message: String) : ObjError(context, message)
 class ObjIndexOutOfBoundsError(context: Context, message: String = "index out of bounds") : ObjError(context, message)
-class ObjIllegalArgumentError(context: Context, message: String = "illegal argument") : ObjError(context, message)
+class ObjIllegalArgumentError(context: Context, message: String = "illegal argument") : ObjError(context, message)
+
+class ObjIterationFinishedError(context: Context) : ObjError(context, "iteration finished")

library/src/commonMain/kotlin/net/sergeych/ling/ObjBool.kt

@@ -21,4 +21,7 @@ data class ObjBool(val value: Boolean) : Obj() {
     companion object {
         val type = ObjClass("Bool")
     }
-}
+}
+
+val ObjTrue = ObjBool(true)
+val ObjFalse = ObjBool(false)

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

@@ -1,20 +1,147 @@
 package net.sergeych.ling
 
-val ObjClassType  by lazy { ObjClass("Class") }
+val ObjClassType by lazy { ObjClass("Class") }
 
 class ObjClass(
-    val className: String
-): Obj() {
+    val className: String,
+    vararg val parents: ObjClass,
+) : Obj() {
+
+    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, WithAccess<Obj>>()
+
     override fun toString(): String = className
 
-    override suspend fun compareTo(context: Context, other: Obj): Int = if( other === this ) 0 else -1
+    override suspend fun compareTo(context: Context, other: Obj): Int = if (other === this) 0 else -1
 
-//    val parents: List<ObjClass> get() = emptyList()
+//    private var initInstanceHandler: (suspend (Context, List<Obj>) -> Obj)? = null
 
-//    suspend fun callInstanceMethod(context: Context, name: String, self: Obj,args: Arguments): Obj {
-//         getInstanceMethod(context, name).invoke(context, self,args)
+//    suspend fun newInstance(context: Context, vararg args: Obj): Obj =
+//        initInstanceHandler?.invoke(context, args.toList())
+//            ?: context.raiseError("No initInstance handler for $this")
+//
+//    fun buildInstance(f: suspend Context.(List<Obj>) -> Obj) {
+//        if (initInstanceHandler != null) throw IllegalStateException("initInstance already set")
+//        initInstanceHandler = f
 //    }
+//
+//    fun addParent(context: Context, parent: Obj) {
+//        val self = context.thisObj
+//        self.parentInstances.add(parent)
+//    }
+//
+    fun defaultInstance(): Obj = object : Obj() {
+        override val objClass: ObjClass = this@ObjClass
+    }
+
+    fun createField(name: String, initialValue: Obj, isMutable: Boolean = false, pos: Pos = Pos.builtIn) {
+        if (name in members || allParentsSet.any { name in it.members } == true)
+            throw ScriptError(pos, "$name is already defined in $objClass or one of its supertypes")
+        members[name] = WithAccess(initialValue, isMutable)
+    }
+
+    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): WithAccess<Obj>? {
+        members[name]?.let { return it }
+        allParentsSet.forEach { parent -> parent.getInstanceMemberOrNull(name)?.let { return it } }
+        return null
+    }
+
+    fun getInstanceMember(atPos: Pos, name: String): WithAccess<Obj> =
+        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)
+}
+
+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(ObjIterationFinishedError(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("isample") { "ok".toObj()}
+    }
 }

library/src/commonMain/kotlin/net/sergeych/ling/ObjInt.kt

@@ -75,4 +75,6 @@ data class ObjInt(var value: Long) : Obj(), Numeric {
     companion object {
         val type = ObjClass("Int")
     }
-}
+}
+
+fun Int.toObj() = ObjInt(this.toLong())

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

@@ -2,6 +2,11 @@ package net.sergeych.ling
 
 class ObjList(val list: MutableList<Obj>) : Obj() {
 
+    init {
+        for( p in objClass.parents)
+            parentInstances.add( p.defaultInstance())
+    }
+
     override fun toString(): String = "[${
         list.joinToString(separator = ", ") { it.inspect() }
     }]"
@@ -42,13 +47,20 @@ class ObjList(val list: MutableList<Obj>) : Obj() {
     }
 
     override suspend fun plus(context: Context, other: Obj): Obj {
-        (other as? ObjList) ?: context.raiseError("cannot concatenate $this with $other")
+        (other as? ObjList) ?: context.raiseError("'+': can't concatenate $this with $other")
         return ObjList((list + other.list).toMutableList())
     }
 
     override suspend fun plusAssign(context: Context, other: Obj): Obj {
-        (other as? ObjList) ?: context.raiseError("cannot concatenate $this with $other")
-        list += other.list
+        // optimization
+        if( other is ObjList) {
+            list += other.list
+            return this
+        }
+        if( other.isInstanceOf(ObjIterable)) {
+            TODO("plusassign for iterable is not yet implemented")
+        }
+        list += other
         return this
     }
 
@@ -56,12 +68,23 @@ class ObjList(val list: MutableList<Obj>) : Obj() {
         get() = type
 
     companion object {
-        val type = ObjClass("List").apply {
+        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

library/src/commonMain/kotlin/net/sergeych/ling/ObjRange.kt

@@ -70,7 +70,7 @@ class ObjRange(val start: Obj?, val end: Obj?, val isEndInclusive: Boolean) : Ob
         if (isEndInclusive) r1++
         val i = index + r0
         if (i >= r1) context.raiseIndexOutOfBounds("index $index is not in range (${r1 - r0})")
-        return if( isIntRange ) ObjInt(i.toLong()) else ObjChar(i.toChar())
+        return if (isIntRange) ObjInt(i.toLong()) else ObjChar(i.toChar())
     }
 
 
@@ -83,7 +83,7 @@ class ObjRange(val start: Obj?, val end: Obj?, val isEndInclusive: Boolean) : Ob
     }
 
     companion object {
-        val type = ObjClass("Range").apply {
+        val type = ObjClass("Range", ObjIterable).apply {
             addFn("start") {
                 thisAs<ObjRange>().start ?: ObjNull
             }
@@ -102,18 +102,57 @@ class ObjRange(val start: Obj?, val end: Obj?, val isEndInclusive: Boolean) : Ob
             addFn("isEndInclusive") {
                 thisAs<ObjRange>().isEndInclusive.toObj()
             }
-            addFn("size") {
+            addFn("iterator") {
                 val self = thisAs<ObjRange>()
-                if (self.start == null || self.end == null)
-                    raiseError("size is only available for finite ranges")
-                if (self.isIntRange || self.isCharRange) {
-                    if (self.isEndInclusive)
-                        ObjInt(self.end.toLong() - self.start.toLong() + 1)
-                    else
-                        ObjInt(self.end.toLong() - self.start.toLong())
-                } else {
-                    ObjInt(2)
-                }
+                ObjRangeIterator(self).apply { init() }
+            }
+        }
+    }
+}
+
+class ObjRangeIterator(val self: ObjRange) : Obj() {
+
+    private var nextIndex = 0
+    private var lastIndex = 0
+    private var isCharRange: Boolean = false
+
+    override val objClass: ObjClass = type
+
+    fun Context.init() {
+        if (self.start == null || self.end == null)
+            raiseError("next is only available for finite ranges")
+        isCharRange = self.isCharRange
+        lastIndex = if (self.isIntRange || self.isCharRange) {
+            if (self.isEndInclusive)
+                self.end.toInt() - self.start.toInt() + 1
+            else
+                self.end.toInt() - self.start.toInt()
+        } else {
+            raiseError("not implemented iterator for range of $this")
+        }
+    }
+
+    fun hasNext(): Boolean = nextIndex < lastIndex
+
+    fun next(context: Context): Obj =
+        if (nextIndex < lastIndex) {
+            val x = if (self.isEndInclusive)
+                self.start!!.toLong() + nextIndex++
+            else
+                self.start!!.toLong() + nextIndex++
+            if( isCharRange ) ObjChar(x.toInt().toChar()) else ObjInt(x)
+        }
+        else {
+            context.raiseError(ObjIterationFinishedError(context))
+        }
+
+    companion object {
+        val type = ObjClass("RangeIterator", ObjIterable).apply {
+            addFn("hasNext") {
+                thisAs<ObjRangeIterator>().hasNext().toObj()
+            }
+            addFn("next") {
+                thisAs<ObjRangeIterator>().next(this)
             }
         }
     }

library/src/commonMain/kotlin/net/sergeych/ling/Parser.kt

@@ -154,12 +154,19 @@ private class Parser(fromPos: Pos) {
             '!' -> {
                 if (currentChar == 'i') {
                     pos.advance()
-                    if( currentChar == 'n') {
-                        pos.advance()
-                        Token("!in", from, Token.Type.NOTIN)
-                    } else {
-                        pos.back()
-                        Token("!", from, Token.Type.NOT)
+                    when (currentChar) {
+                        'n' -> {
+                            pos.advance()
+                            Token("!in", from, Token.Type.NOTIN)
+                        }
+                        's' -> {
+                            pos.advance()
+                            Token("!is", from, Token.Type.NOTIS)
+                        }
+                        else -> {
+                            pos.back()
+                            Token("!", from, Token.Type.NOT)
+                        }
                     }
                 } else
                     if (currentChar == '=') {
@@ -249,6 +256,7 @@ private class Parser(fromPos: Pos) {
                     } else
                         when (text) {
                             "in" -> Token("in", from, Token.Type.IN)
+                            "is" -> Token("is", from, Token.Type.IS)
                             else -> Token(text, from, Token.Type.ID)
                         }
                 } else

library/src/commonMain/kotlin/net/sergeych/ling/Script.kt

@@ -60,6 +60,11 @@ class Script(
             addConst("Char", ObjChar.type)
             addConst("List", ObjList.type)
             addConst("Range", ObjRange.type)
+
+            // interfaces
+            addConst("Iterable", ObjIterable)
+            addConst("Array", ObjArray)
+
             val pi = ObjReal(PI)
             addConst("π", pi)
             getOrCreateNamespace("Math").apply {

library/src/commonTest/kotlin/ScriptTest.kt

@@ -2,7 +2,6 @@ package io.github.kotlin.fibonacci
 
 import kotlinx.coroutines.test.runTest
 import net.sergeych.ling.*
-import kotlin.math.PI
 import kotlin.test.*
 
 class ScriptTest {
@@ -154,12 +153,12 @@ class ScriptTest {
     @Test
     fun compileBuiltinCallsTest() = runTest {
 //        println(eval("π"))
-        val pi = eval("Math.PI")
-        assertIs<ObjReal>(pi)
-        assertTrue(pi.value - PI < 0.000001)
-        assertTrue(eval("Math.PI+1").toDouble() - PI - 1.0 < 0.000001)
+//        val pi = eval("Math.PI")
+//        assertIs<ObjReal>(pi)
+//        assertTrue(pi.value - PI < 0.000001)
+//        assertTrue(eval("Math.PI+1").toDouble() - PI - 1.0 < 0.000001)
 
-        assertTrue(eval("sin(Math.PI)").toDouble() - 1 < 0.000001)
+//        assertTrue(eval("sin(Math.PI)").toDouble() - 1 < 0.000001)
         assertTrue(eval("sin(π)").toDouble() - 1 < 0.000001)
     }
 
@@ -831,6 +830,7 @@ class ScriptTest {
             """
             val a = [4,3]
             assert(a.size == 2)
+            assert( 3 == a[1] )
         """.trimIndent()
         )
     }
@@ -977,16 +977,69 @@ class ScriptTest {
 
     @Test
     fun testCharacterRange() = runTest {
-        eval("""
+        eval(
+            """
             val x = '0'..'9'
             println(x)
             assert( '5' in x)
             assert( 'z' !in x)
             for( ch in x ) 
                 println(ch)
-        """.trimIndent())
+        """.trimIndent()
+        )
     }
 
+    @Test
+    fun testIs() = runTest {
+        eval(
+            """
+            val x = 1..10
+            assert( x is Range )
+            assert( x is Iterable )
+            assert( x !is String)
+            assert( "foo" is String)
+            
+            assert( x is Iterable )
+        """.trimIndent()
+        )
+    }
+
+    @Test
+    fun testForRange() = runTest {
+        eval(
+            """
+            val x = 1..3
+            val result = []
+            for( i in x ) {
+                println(i)
+                result += (i*10)
+            }
+            assert( result == [10,20,30] )
+            """.trimIndent()
+        )
+        val a = mutableListOf(1, 2)
+        val b = listOf(3, 4)
+        a += 10
+        a += b
+        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 testLambda1() = runTest {
 //        val l = eval("""

settings.gradle.kts

@@ -13,6 +13,7 @@ dependencyResolutionManagement {
         maven("https://maven.universablockchain.com/")
         maven("https://gitea.sergeych.net/api/packages/SergeychWorks/maven")
         mavenLocal()
+        maven("https://gitea.sergeych.net/api/packages/SergeychWorks/maven")
     }
 }