associateBy and Lyng:Iterable .toFlow() for kotlin integration simplicity

docs/Iterable.md

@@ -21,6 +21,20 @@ Having `Iterable` in base classes allows to use it in for loop. Also, each `Iter
 
 ## Instance methods
 
+| fun/method      | description                                                                     |
+|-----------------|---------------------------------------------------------------------------------|
+| toList()        | create a list from iterable                                                     |
+| toSet()         | create a set from iterable                                                      |
+| contains(i)     | check that iterable contains `i`                                                |
+| `i in iterator` | same as `contains(i)`                                                           |
+| isEmpty()       | check iterable is empty                                                         |
+| forEach(f)      | call f for each element                                                         |
+| toMap()         | create a map from list of key-value pairs (arrays of 2 items or like)           |
+| map(f)          | create a list of values returned by `f` called for each element of the iterable |
+| indexOf(i)      | return index if the first encounter of i or a negative value if not found       |
+| associateBy(kf) | create a map where keys are returned by kf that will be called for each element |
+
+
     fun Iterable.toList(): List
     fun Iterable.toSet(): Set
     fun Iterable.indexOf(element): Int
@@ -28,6 +42,7 @@ Having `Iterable` in base classes allows to use it in for loop. Also, each `Iter
     fun Iterable.isEmpty(element): Bool
     fun Iterable.forEach(block: (Any?)->Void ): Void
     fun Iterable.map(block: (Any?)->Void ): List
+    fun Iterable.associateBy( keyMaker: (Any?)->Any): Map
     
 
 ## Abstract methods

docs/tutorial.md

@@ -1215,7 +1215,7 @@ Typical set of String functions includes:
 | s1 + s2            | concatenation                                              |
 | s1 += s2           | self-modifying concatenation                               |
 | toReal()           | attempts to parse string as a Real value                   |
-|                    |                                                            |
+| toInt()            | parse string to Int value                                  |
 |                    |                                                            |
 
 

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

@@ -158,7 +158,6 @@ class Compiler(
                                     isCall = true
                                     val lambda =
                                         parseLambdaExpression(cc)
-                                    println(cc.current())
                                     operand = Accessor { context ->
                                         context.pos = next.pos
                                         val v = left.getter(context).value

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

@@ -87,6 +87,14 @@ open class Obj {
         // note that getInstanceMember traverses the hierarchy
         objClass.getInstanceMember(context.pos, name).value.invoke(context, this, args)
 
+    open suspend fun getInstanceMethod(
+        context: Context,
+        name: String,
+        args: Arguments = Arguments.EMPTY
+    ): Obj =
+        // note that getInstanceMember traverses the hierarchy
+        objClass.getInstanceMember(context.pos, name).value
+
     fun getMemberOrNull(name: String): Obj? = objClass.getInstanceMemberOrNull(name)?.value
 
     // methods that to override
@@ -210,6 +218,8 @@ open class Obj {
         context.raiseNotImplemented("indexing")
     }
 
+    suspend fun getAt(context: Context, index: Int): Obj = getAt(context, ObjInt(index.toLong()))
+
     open suspend fun putAt(context: Context, index: Int, newValue: Obj) {
         context.raiseNotImplemented("indexing")
     }

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

@@ -48,12 +48,20 @@ val ObjIterable by lazy {
         }
 
         addFn("toMap") {
-            val result = mutableListOf<Obj>()
-            val it = thisObj.invokeInstanceMethod(this, "iterator")
-            while (it.invokeInstanceMethod(this, "hasNext").toBool()) {
-                result += it.invokeInstanceMethod(this, "next")
+            val result = ObjMap()
+            thisObj.toFlow(this).collect { pair ->
+                result.map[pair.getAt(this,0)] = pair.getAt(this, 1)
             }
-            ObjMap(ObjMap.listToMap(this, result))
+            result
+        }
+
+        addFn("associateBy") {
+            val association = requireOnlyArg<Statement>()
+            val result = ObjMap()
+            thisObj.toFlow(this).collect {
+                result.map[association.call(this, it)] = it
+            }
+            result
         }
 
         addFn("forEach", isOpen = true) {
@@ -67,12 +75,10 @@ val ObjIterable by lazy {
         }
 
         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))))
+            thisObj.toFlow(this).collect {
+                result += fn.call(this, it)
             }
             ObjList(result)
         }

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

@@ -2,6 +2,9 @@
 
 package net.sergeych.lyng
 
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flow
+
 /**
  * Iterator wrapper to allow Kotlin collections to be returned from Lyng objects;
  * each object is converted to a Lyng object.
@@ -37,3 +40,18 @@ class ObjKotlinObjIterator(val iterator: Iterator<Obj>) : Obj() {
 
     }
 }
+
+/**
+ * Convert Lyng's Iterable to Kotlin's Flow.
+ *
+ * As Lyng is totally asynchronous, its iterator can't be trivially converted to Kotlin's synchronous iterator.
+ * It is, though, trivially convertible to Kotlin's Flow.
+ */
+fun Obj.toFlow(context: Context): Flow<Obj> = flow {
+    val iterator = invokeInstanceMethod(context, "iterator")
+    val hasNext = iterator.getInstanceMethod(context, "hasNext")
+    val next = iterator.getInstanceMethod(context, "next")
+    while (hasNext.invoke(context, iterator).toBool()) {
+        emit(next.invoke(context, iterator))
+    }
+}

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

@@ -34,7 +34,7 @@ class ObjMapEntry(val key: Obj, val value: Obj) : Obj() {
     }
 }
 
-class ObjMap(val map: MutableMap<Obj, Obj>) : Obj() {
+class ObjMap(val map: MutableMap<Obj, Obj> = mutableMapOf()) : Obj() {
 
     override val objClass = type
 

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

@@ -76,6 +76,9 @@ data class ObjString(val value: String) : Obj() {
 
     companion object {
         val type = ObjClass("String").apply {
+            addFn("toInt") {
+                ObjInt(thisAs<ObjString>().value.toLong())
+            }
             addFn("startsWith") {
                 ObjBool(thisAs<ObjString>().value.startsWith(requiredArg<ObjString>(0).value))
             }

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

@@ -34,6 +34,8 @@ abstract class Statement(
         val type = ObjClass("Callable")
     }
 
+    suspend fun call(context: Context,vararg args: Obj) = execute(context.copy(args =  Arguments(*args)))
+
 }
 
 fun Statement.raise(text: String): Nothing {

lynglib/src/commonTest/kotlin/ScriptTest.kt

@@ -1,4 +1,6 @@
 
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.toList
 import kotlinx.coroutines.test.runTest
 import net.sergeych.lyng.*
 import kotlin.test.*
@@ -2311,4 +2313,23 @@ class ScriptTest {
             assert( ! "5.2".isInteger() )
         """.trimIndent())
     }
+
+    @Test
+    fun testToFlow() = runTest() {
+        val c = Context()
+        val arr = c.eval("[1,2,3]")
+        // array is iterable so we can:
+        assertEquals(listOf(1,2,3),  arr.toFlow(c).map { it.toInt() }.toList())
+    }
+
+    @Test
+    fun testAssociateBy() = runTest() {
+        eval("""
+            val m = [123, 456].associateBy { "k:%s"(it) }
+            println(m)
+            assertEquals(123, m["k:123"])
+            assertEquals(456, m["k:456"])
+            """)
+        listOf(1,2,3).associateBy { it * 10 }
+    }
 }