optimize arithmetics

docs/Range.md

@@ -140,7 +140,7 @@ Open-ended ranges require an explicit step to iterate:
 
 You can use Char as both ends of the closed range:
 
-    val r = 'a' .. 'c'
+    val r = 'a'..'c'
     assert( 'b' in r)
     assert( 'e' !in r)
     for( ch in r )

docs/pi_spigot_perf_baseline.md

@@ -0,0 +1,62 @@
+## Pi Spigot JVM Baseline
+
+Saved on April 4, 2026 before the `List<Int>` indexed-access follow-up fix.
+
+Benchmark target:
+- [examples/pi-bench.py](/home/sergeych/dev/lyng/examples/pi-bench.py)
+- [examples/pi-bench.lyng](/home/sergeych/dev/lyng/examples/pi-bench.lyng)
+
+Execution path:
+- Python: `python3 examples/pi-bench.py`
+- Lyng JVM: `./gradlew :lyng:runJvm --args='/home/sergeych/dev/lyng/examples/pi-bench.lyng'`
+- Constraint: do not use Kotlin/Native `lyng` CLI for perf comparisons
+
+Baseline measurements:
+- Python full script: `167 ms`
+- Lyng JVM full script: `1.287097604 s`
+- Python warm function average over 5 runs: `126.126 ms`
+- Lyng JVM warm function average over 5 runs: about `1071.6 ms`
+
+Baseline ratio:
+- Full script: about `7.7x` slower on Lyng JVM
+- Warm function only: about `8.5x` slower on Lyng JVM
+
+Primary finding at baseline:
+- The hot `reminders[j]` accesses in `piSpigot` were still lowered through boxed object index ops and boxed arithmetic.
+- Newly added `GET_INDEX_INT` and `SET_INDEX_INT` only reached `pi`, not `reminders`.
+- Root cause: initializer element inference handled list literals, but not `List.fill(boxes) { 2 }`, so `reminders` did not become known `List<Int>` at compile time.
+
+## After Optimizations 1-4
+
+Follow-up change:
+- propagate inferred lambda return class into bytecode compilation
+- infer `List.fill(...)` element type from the fill lambda
+- lower `reminders[j]` reads and writes to `GET_INDEX_INT` and `SET_INDEX_INT`
+- add primitive-backed `ObjList` storage for all-int lists
+- lower `List.fill(Int) { Int }` to `LIST_FILL_INT`
+- stop boxing the integer index inside `GET_INDEX_INT` / `SET_INDEX_INT`
+
+Verification:
+- `piSpigot` disassembly now contains typed ops for `reminders`, for example:
+  - `GET_INDEX_INT s5(reminders), s10(j), ...`
+  - `SET_INDEX_INT s5(reminders), s10(j), ...`
+
+Post-change measurements using `jlyng`:
+- Full script: `655.819559 ms`
+- Warm 5-run total: `1.430945810 s`
+- Warm average per run: about `286.2 ms`
+
+Observed improvement vs baseline:
+- Full script: about `1.96x` faster (`1.287 s -> 0.656 s`)
+- Warm function: about `3.74x` faster (`1071.6 ms -> 286.2 ms`)
+
+Residual gap vs Python baseline:
+- Full script: Lyng JVM is still about `3.9x` slower than Python (`655.8 ms` vs `167 ms`)
+- Warm function: Lyng JVM is still about `2.3x` slower than Python (`286.2 ms` vs `126.126 ms`)
+
+Current benchmark-test snapshot (`n=200`, JVM test harness):
+- `optimized-int-division-rval-off`: `135 ms`
+- `optimized-int-division-rval-on`: `125 ms`
+- `piSpigot` bytecode now contains:
+  - `LIST_FILL_INT` for both `pi` and `reminders`
+  - `GET_INDEX_INT` / `SET_INDEX_INT` for the hot indexed loop

docs/tutorial.md

@@ -1531,11 +1531,9 @@ It could be open and closed:
 
 Descending ranges are explicit too:
 
-    (5 downTo 1).toList()
+    assertEquals([5,4,3,2,1], (5 downTo 1).toList())
-    >>> [5,4,3,2,1]
+    assertEquals([5,4,3,2], (5 downUntil 1).toList())
-
+    >>> void
-    (5 downUntil 1).toList()
-    >>> [5,4,3,2]
 
 Ranges could be inside other ranges:
 
@@ -1549,7 +1547,7 @@ There are character ranges too:
 
 and you can use ranges in for-loops:
 
-    for( x in 'a' ..< 'c' ) println(x)
+    for( x in 'a'..<'c' ) println(x)
     >>> a
     >>> b
     >>> void

examples/pi-bench.lyng

@@ -1,18 +1,18 @@
 import lyng.time
 
-val WORK_SIZE = 200
+val WORK_SIZE = 500
-val TASK_COUNT = 10
+val THREADS = 1
 
 fn piSpigot(iThread: Int, n: Int) {
-    var pi = []
+    var piIter = 0
+    var pi = List.fill(n) { 0 }
     val boxes = n * 10 / 3
     var reminders = List.fill(boxes) { 2 }
     var heldDigits = 0
-    for (i in 0..n) {
+    for (i in 0..<n) {
         var carriedOver = 0
         var sum = 0
-        for (k in 1..boxes) {
+        for (j in (boxes - 1) downTo 0) {
-            val j = boxes - k
             val denom = j * 2 + 1
             reminders[j] *= 10
             sum = reminders[j] + carriedOver
@@ -39,29 +39,29 @@ fn piSpigot(iThread: Int, n: Int) {
         } else {
             heldDigits = 1
         }
-        pi.add(q)
+        pi[piIter] = q
+        ++piIter
     }
 
-    var s = ""
+    var res = ""
     for (i in (n - 8)..<n) {
-        s += pi[i]
+        res += pi[i]
     }
 
-    println(iThread, " - done: ", s)
+    println(iThread.toString() + ": " + res)
+    res
 }
 
-var counter = 0
+for( r in 0..100 ) {
+    val t0 = Instant()
 
-val t0 = Instant()
+    println("piBench (lyng): THREADS = " + THREADS + ", WORK_SIZE = " + WORK_SIZE)
-(1..TASK_COUNT).map { n ->
+    for (i in 0..<THREADS) {
-    val counterState = counter
+        piSpigot(i, WORK_SIZE)
-    val t = launch {
-        piSpigot(counterState, WORK_SIZE)
     }
-    ++counter
-    t
-}.forEach { (it as Deferred).await() }
 
-val dt = Instant() - t0
+    val dt = Instant() - t0
 
-println("all done, dt = ", dt)
+    println("all done, dt = ", dt)
+    delay(800)
+}

examples/pi-bench.py

@@ -0,0 +1,83 @@
+#  Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+
+import time
+from multiprocessing import Process
+
+def piSpigot(iThread, nx):
+    piIter = 0
+    pi = [None] * nx
+    boxes = nx * 10 // 3
+    reminders = [None]*boxes
+    i = 0
+    while i < boxes:
+        reminders[i] = 2
+        i += 1
+    heldDigits = 0
+    i = 0
+    while i < nx:
+        carriedOver = 0
+        sum = 0
+        j = boxes - 1
+        while j >= 0:
+            reminders[j] *= 10
+            sum = reminders[j] + carriedOver
+            quotient = sum // (j * 2 + 1)
+            reminders[j] = sum % (j * 2 + 1)
+            carriedOver = quotient * j
+            j -= 1
+        reminders[0] = sum % 10
+        q = sum // 10
+        if q == 9:
+            heldDigits += 1
+        elif q == 10:
+            q = 0
+            k = 1
+            while k <= heldDigits:
+                replaced = pi[i - k]
+                if replaced == 9:
+                    replaced = 0
+                else:
+                    replaced += 1
+                pi[i - k] = replaced
+                k += 1
+            heldDigits = 1
+        else:
+            heldDigits = 1
+        pi[piIter] = q
+        piIter += 1
+        i += 1
+    res = ""
+    for i in range(len(pi)-8, len(pi), 1):
+        res += str(pi[i])
+    print(str(iThread) + ": " + res)
+
+def createProcesses():
+    THREADS = 1
+    WORK_SIZE = 500
+    print("piBench (python3): THREADS = " + str(THREADS) + ", WORK_SIZE = " + str(WORK_SIZE))
+    pa = []
+    for i in range(THREADS):
+        p = Process(target=piSpigot, args=(i, WORK_SIZE))
+        p.start()
+        pa.append(p)
+    for p in pa:
+        p.join()
+
+if __name__ == "__main__":
+    t1 = time.time()
+    createProcesses()
+    dt = time.time() - t1
+    print("total time: %i ms" % (dt*1000))

examples/pi-test.lyng

@@ -1,49 +0,0 @@
-fn piSpigot(n) {
-  var pi = []
-  val boxes = n * 10 / 3
-  var reminders = []
-  for (i in 0..<boxes) {
-    reminders.add(2)
-  }
-  var heldDigits = 0
-  for (i in 0..n) {
-    var carriedOver = 0
-    var sum = 0
-    for (k in 1..boxes) {
-      val j = boxes - k
-      val denom = j * 2 + 1
-      reminders[j] *= 10
-      sum = reminders[j] + carriedOver
-      // Keep this integer-only. Real coercion here is much slower in the hot loop.
-      val quotient = sum / denom
-      reminders[j] = sum % denom
-      carriedOver = quotient * j
-    }
-    reminders[0] = sum % 10
-    var q = sum / 10
-    if (q == 9) {
-      ++heldDigits
-    } else if (q == 10) {
-      q = 0
-      for (k in 1..heldDigits) {
-        var replaced = pi[i - k]
-        if (replaced == 9) {
-          replaced = 0
-        } else {
-          ++replaced
-        }
-        pi[i - k] = replaced
-      }
-      heldDigits = 1
-    } else {
-      heldDigits = 1
-    }
-    pi.add(q)
-  }
-
-  var suffix = ""
-  for (i in (n - 8)..<n) {
-    suffix += pi[i]
-  }
-  suffix
-}

lyng/src/jvmTest/kotlin/net/sergeych/CliDispatcherJvmTest.kt

@@ -20,9 +20,11 @@ import kotlinx.coroutines.runBlocking
 import net.sergeych.lyng.EvalSession
 import net.sergeych.lyng.Script
 import net.sergeych.lyng.Source
+import net.sergeych.lyng.obj.ObjInt
 import net.sergeych.lyng.obj.ObjList
 import net.sergeych.lyng.obj.ObjString
 import org.junit.Test
+import kotlin.test.assertEquals
 import kotlin.test.assertNotEquals
 
 class CliDispatcherJvmTest {
@@ -69,4 +71,34 @@ class CliDispatcherJvmTest {
             session.cancelAndJoin()
         }
     }
+
+    @Test
+    fun cliEvalInfersDeferredItTypeFromMapLambdaLocal() = runBlocking {
+        val session = EvalSession(Script.newScope())
+        try {
+            val result = evalOnCliDispatcher(
+                session,
+                Source(
+                    "<cli-repro>",
+                    """
+                    var sum = 0
+                    var counter = 0
+
+                    (1..3).map { n ->
+                        val counterState = counter
+                        val task = launch { counterState + n }
+                        ++counter
+                        task
+                    }.forEach { sum += it.await() }
+
+                    sum
+                    """.trimIndent()
+                )
+            )
+
+            assertEquals(9, (result as ObjInt).value)
+        } finally {
+            session.cancelAndJoin()
+        }
+    }
 }

lyngio/src/commonTest/kotlin/net/sergeych/lyng/io/net/LyngNetTcpServerExampleTest.kt

@@ -17,7 +17,9 @@
 
 package net.sergeych.lyng.io.net
 
-import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.test.runTest
+import kotlinx.coroutines.withContext
 import kotlinx.coroutines.withTimeout
 import net.sergeych.lyng.Compiler
 import net.sergeych.lyng.Script
@@ -29,9 +31,9 @@ import kotlin.test.assertEquals
 class LyngNetTcpServerExampleTest {
 
     @Test
-    fun tcpServerExampleRoundTripsOverLoopback() = runBlocking {
+    fun tcpServerExampleRoundTripsOverLoopback() = runTest {
         val engine = getSystemNetEngine()
-        if (!engine.isSupported || !engine.isTcpAvailable || !engine.isTcpServerAvailable) return@runBlocking
+        if (!engine.isSupported || !engine.isTcpAvailable || !engine.isTcpServerAvailable) return@runTest
 
         val scope = Script.newScope()
         createNetModule(PermitAllNetAccessPolicy, scope)
@@ -60,8 +62,10 @@ class LyngNetTcpServerExampleTest {
             "${'$'}{accepted.await()}: ${'$'}reply"
         """.trimIndent()
 
-        val result = withTimeout(5_000) {
+        val result = withContext(Dispatchers.Default) {
-            Compiler.compile(code).execute(scope).inspect(scope)
+            withTimeout(5_000) {
+                Compiler.compile(code).execute(scope).inspect(scope)
+            }
         }
 
         assertEquals("\"ping: echo:ping\"", result)

lyngio/src/jsNodeTest/kotlin/net/sergeych/lyng/io/net/LyngNetModuleJsNodeTest.kt

@@ -1,3 +1,20 @@
+/*
+ * Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
 package net.sergeych.lyng.io.net
 
 import kotlinx.coroutines.DelicateCoroutinesApi

lyngio/src/jsNodeTest/kotlin/net/sergeych/lyngio/NetJsNodeTest.kt

@@ -1,3 +1,20 @@
+/*
+ * Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
 package net.sergeych.lyngio
 
 import kotlinx.coroutines.DelicateCoroutinesApi

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

@@ -170,6 +170,20 @@ class Compiler(
     private val typeAliases: MutableMap<String, TypeAliasDecl> = mutableMapOf()
     private val methodReturnTypeDeclByRef: MutableMap<ObjRef, TypeDecl> = mutableMapOf()
     private val callReturnTypeDeclByRef: MutableMap<CallRef, TypeDecl> = mutableMapOf()
+    private val iterableLikeTypeNames = setOf(
+        "Iterable",
+        "Collection",
+        "Array",
+        "List",
+        "ImmutableList",
+        "Set",
+        "ImmutableSet",
+        "Flow",
+        "ObservableList",
+        "RingBuffer",
+        "Range",
+        "IntRange"
+    )
     private val callableReturnTypeByScopeId: MutableMap<Int, MutableMap<Int, ObjClass>> = mutableMapOf()
     private val callableReturnTypeByName: MutableMap<String, ObjClass> = mutableMapOf()
     private val callableReturnTypeDeclByName: MutableMap<String, TypeDecl> = mutableMapOf()
@@ -2721,7 +2735,7 @@ class Compiler(
                                 Token.Type.LPAREN -> {
                                     cc.next()
                                     if (shouldTreatAsClassScopeCall(left, next.value)) {
-                                        val parsed = parseArgs(null)
+                                        val parsed = parseArgs(null, implicitItTypeNameForMemberLambda(left, next.value))
                                         val args = parsed.first
                                         val tailBlock = parsed.second
                                         isCall = true
@@ -2738,7 +2752,7 @@ class Compiler(
                                         val receiverType = if (next.value == "apply" || next.value == "run") {
                                             inferReceiverTypeFromRef(left)
                                         } else null
-                                        val parsed = parseArgs(receiverType)
+                                        val parsed = parseArgs(receiverType, implicitItTypeNameForMemberLambda(left, next.value))
                                         val args = parsed.first
                                         val tailBlock = parsed.second
                                         if (left is LocalVarRef && left.name == "scope") {
@@ -2807,9 +2821,7 @@ class Compiler(
                                     val receiverType = if (next.value == "apply" || next.value == "run") {
                                         inferReceiverTypeFromRef(left)
                                     } else null
-                                    val itType = if (next.value == "let" || next.value == "also") {
+                                    val itType = implicitItTypeNameForMemberLambda(left, next.value)
-                                        inferReceiverTypeFromRef(left)
-                                    } else null
                                     val lambda = parseLambdaExpression(receiverType, implicitItType = itType)
                                     val argPos = next.pos
                                     val args = listOf(ParsedArgument(ExpressionStatement(lambda, argPos), next.pos))
@@ -3239,6 +3251,8 @@ class Compiler(
             if (cls != null && itSlot != null) {
                 val paramTypeMap = slotTypeByScopeId.getOrPut(paramSlotPlan.id) { mutableMapOf() }
                 paramTypeMap[itSlot] = cls
+                val paramTypeDeclMap = slotTypeDeclByScopeId.getOrPut(paramSlotPlan.id) { mutableMapOf() }
+                paramTypeDeclMap[itSlot] = TypeDecl.Simple(implicitItType, false)
             }
         }
 
@@ -3384,7 +3398,12 @@ class Compiler(
                             }
                             val itSlot = slotPlan["it"]
                             if (itSlot != null) {
-                                frame.frame.setObj(itSlot, itValue)
+                                when (itValue) {
+                                    is ObjInt -> frame.frame.setInt(itSlot, itValue.value)
+                                    is ObjReal -> frame.frame.setReal(itSlot, itValue.value)
+                                    is ObjBool -> frame.frame.setBool(itSlot, itValue.value)
+                                    else -> frame.frame.setObj(itSlot, itValue)
+                                }
                             }
                         } else {
                             argsDeclaration.assignToFrame(
@@ -3414,6 +3433,7 @@ class Compiler(
             paramSlotPlan = paramSlotPlanSnapshot,
             argsDeclaration = argsDeclaration,
             captureEntries = captureEntries,
+            inferredReturnClass = returnClass,
             preferredThisType = expectedReceiverType,
             wrapAsExtensionCallable = wrapAsExtensionCallable,
             returnLabels = returnLabels,
@@ -4771,7 +4791,7 @@ class Compiler(
                 val targetClass = resolveReceiverClassForMember(ref.targetRef)
                 classMethodReturnTypeDecl(targetClass, "getAt")
             }
-            is MethodCallRef -> methodReturnTypeDeclByRef[ref]
+            is MethodCallRef -> methodReturnTypeDeclByRef[ref] ?: inferMethodCallReturnTypeDecl(ref)
             is CallRef -> callReturnTypeDeclByRef[ref] ?: inferCallReturnTypeDecl(ref)
             is BinaryOpRef -> inferBinaryOpReturnTypeDecl(ref)
             is StatementRef -> (ref.statement as? ExpressionStatement)?.let { resolveReceiverTypeDecl(it.ref) }
@@ -5012,8 +5032,7 @@ class Compiler(
     }
 
     private fun inferMethodCallReturnClass(ref: MethodCallRef): ObjClass? {
-        val receiverDecl = resolveReceiverTypeDecl(ref.receiver)
+        val genericReturnDecl = inferMethodCallReturnTypeDecl(ref)
-        val genericReturnDecl = inferMethodCallReturnTypeDecl(ref.name, receiverDecl)
         if (genericReturnDecl != null) {
             methodReturnTypeDeclByRef[ref] = genericReturnDecl
             resolveTypeDeclObjClass(genericReturnDecl)?.let { return it }
@@ -5034,7 +5053,24 @@ class Compiler(
         return inferMethodCallReturnClass(ref.name)
     }
 
+    private fun inferMethodCallReturnTypeDecl(ref: MethodCallRef): TypeDecl? {
+        methodReturnTypeDeclByRef[ref]?.let { return it }
+        val inferred = inferMethodCallReturnTypeDecl(ref.name, resolveReceiverTypeDecl(ref.receiver), ref.args)
+        if (inferred != null) {
+            methodReturnTypeDeclByRef[ref] = inferred
+        }
+        return inferred
+    }
+
     private fun inferMethodCallReturnTypeDecl(name: String, receiver: TypeDecl?): TypeDecl? {
+        return inferMethodCallReturnTypeDecl(name, receiver, emptyList())
+    }
+
+    private fun inferMethodCallReturnTypeDecl(
+        name: String,
+        receiver: TypeDecl?,
+        args: List<ParsedArgument>
+    ): TypeDecl? {
         val base = when (receiver) {
             is TypeDecl.Generic -> receiver.name.substringAfterLast('.')
             is TypeDecl.Simple -> receiver.name.substringAfterLast('.')
@@ -5048,6 +5084,10 @@ class Compiler(
             name == "next" && receiver is TypeDecl.Generic && base == "Iterator" -> {
                 receiver.args.firstOrNull()
             }
+            name == "map" && base in iterableLikeTypeNames -> {
+                val mappedType = args.firstOrNull()?.let { inferCallableReturnTypeDeclFromArgument(it) } ?: TypeDecl.TypeAny
+                TypeDecl.Generic("List", listOf(mappedType), false)
+            }
             name == "toImmutableList" && receiver is TypeDecl.Generic && (base == "Iterable" || base == "Collection" || base == "Array" || base == "List" || base == "ImmutableList") -> {
                 val arg = receiver.args.firstOrNull() ?: TypeDecl.TypeAny
                 TypeDecl.Generic("ImmutableList", listOf(arg), false)
@@ -5120,6 +5160,79 @@ class Compiler(
         }
     }
 
+    private fun inferCallableReturnTypeDeclFromArgument(arg: ParsedArgument): TypeDecl? {
+        val stmt = arg.value as? ExpressionStatement ?: return null
+        val ref = stmt.ref
+        val fnType = inferTypeDeclFromRef(ref) as? TypeDecl.Function
+        if (fnType != null) {
+            return fnType.returnType
+        }
+        return when (ref) {
+            is ValueFnRef -> lambdaReturnTypeByRef[ref]?.let { TypeDecl.Simple(it.className, false) }
+            is ClassOperatorRef -> lambdaReturnTypeByRef[ref]?.let { TypeDecl.Simple(it.className, false) }
+            else -> null
+        }
+    }
+
+    private fun inferIterableElementTypeDecl(receiver: TypeDecl?): TypeDecl? {
+        return when (receiver) {
+            is TypeDecl.Generic -> {
+                val base = receiver.name.substringAfterLast('.')
+                when {
+                    base in iterableLikeTypeNames -> receiver.args.firstOrNull() ?: TypeDecl.TypeAny
+                    else -> null
+                }
+            }
+            is TypeDecl.Simple -> when (receiver.name.substringAfterLast('.')) {
+                "Range", "IntRange" -> TypeDecl.Simple("Int", false)
+                "String" -> TypeDecl.Simple("Char", false)
+                else -> null
+            }
+            else -> null
+        }
+    }
+
+    private fun inferIterableElementTypeDecl(receiver: ObjRef): TypeDecl? {
+        inferIterableElementTypeDecl(inferTypeDeclFromRef(receiver) ?: resolveReceiverTypeDecl(receiver))?.let {
+            return it
+        }
+        return when (receiver) {
+            is MethodCallRef -> if (receiver.name == "map") {
+                receiver.args.firstOrNull()?.let { inferCallableReturnTypeDeclFromArgument(it) }
+            } else {
+                null
+            }
+            else -> null
+        }
+    }
+
+    private fun implicitItTypeNameForMemberLambda(receiver: ObjRef, memberName: String): String? {
+        if (memberName == "fill" && isListTypeRef(receiver)) {
+            return "Int"
+        }
+        if (memberName == "let" || memberName == "also") {
+            return inferReceiverTypeFromRef(receiver)
+        }
+        val typeDecl = when (memberName) {
+            "forEach", "map" -> inferIterableElementTypeDecl(receiver)
+            else -> null
+        } ?: return null
+        return when (typeDecl) {
+            is TypeDecl.Simple -> typeDecl.name.substringAfterLast('.')
+            is TypeDecl.Generic -> typeDecl.name.substringAfterLast('.')
+            else -> resolveTypeDeclObjClass(typeDecl)?.className
+        }
+    }
+
+    private fun isListTypeRef(ref: ObjRef): Boolean {
+        return when (ref) {
+            is LocalVarRef -> ref.name == "List"
+            is LocalSlotRef -> ref.name == "List"
+            is FastLocalVarRef -> ref.name == "List"
+            else -> false
+        }
+    }
+
     private fun inferEncodedPayloadClass(args: List<ParsedArgument>): ObjClass? {
         val stmt = args.firstOrNull()?.value as? ExpressionStatement ?: return null
         val ref = stmt.ref
@@ -6112,7 +6225,10 @@ class Compiler(
      * Parse arguments list during the call and detect last block argument
      * _following the parenthesis_ call: `(1,2) { ... }`
      */
-    private suspend fun parseArgs(expectedTailBlockReceiver: String? = null): Pair<List<ParsedArgument>, Boolean> {
+    private suspend fun parseArgs(
+        expectedTailBlockReceiver: String? = null,
+        implicitItType: String? = null
+    ): Pair<List<ParsedArgument>, Boolean> {
 
         val args = mutableListOf<ParsedArgument>()
         suspend fun tryParseNamedArg(): ParsedArgument? {
@@ -6169,7 +6285,7 @@ class Compiler(
         var lastBlockArgument = false
         if (end.type == Token.Type.LBRACE) {
             // last argument - callable
-            val callableAccessor = parseLambdaExpression(expectedTailBlockReceiver)
+            val callableAccessor = parseLambdaExpression(expectedTailBlockReceiver, implicitItType = implicitItType)
             args += ParsedArgument(
                 ExpressionStatement(callableAccessor, end.pos),
                 end.pos
@@ -8891,6 +9007,12 @@ class Compiler(
             is ListLiteralRef -> ObjList.type
             is MapLiteralRef -> ObjMap.type
             is RangeRef -> ObjRange.type
+            is LocalVarRef -> resolveReceiverTypeDecl(directRef)?.let { resolveTypeDeclObjClass(it) }
+                ?: inferObjClassFromRef(directRef)
+            is FastLocalVarRef -> resolveReceiverTypeDecl(directRef)?.let { resolveTypeDeclObjClass(it) }
+                ?: inferObjClassFromRef(directRef)
+            is LocalSlotRef -> resolveReceiverTypeDecl(directRef)?.let { resolveTypeDeclObjClass(it) }
+                ?: inferObjClassFromRef(directRef)
             is StatementRef -> {
                 val decl = directRef.statement as? ClassDeclStatement
                 decl?.let { resolveClassByName(it.typeName) }

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bytecode/BytecodeCompiler.kt

@@ -2713,9 +2713,14 @@ class BytecodeCompiler(
         }
         if (target is IndexRef) {
             val receiver = compileRefWithFallback(target.targetRef, null, Pos.builtIn) ?: return null
+            val elementSlotType = indexElementSlotType(receiver.slot, target.targetRef)
             if (!target.optionalRef) {
                 val index = compileRefWithFallback(target.indexRef, null, Pos.builtIn) ?: return null
-                builder.emit(Opcode.SET_INDEX, receiver.slot, index.slot, value.slot)
+                if (elementSlotType == SlotType.INT && index.type == SlotType.INT && value.type == SlotType.INT) {
+                    builder.emit(Opcode.SET_INDEX_INT, receiver.slot, index.slot, value.slot)
+                } else {
+                    builder.emit(Opcode.SET_INDEX, receiver.slot, index.slot, value.slot)
+                }
                 noteListElementClassMutation(receiver.slot, value)
             } else {
                 val nullSlot = allocSlot()
@@ -2728,7 +2733,11 @@ class BytecodeCompiler(
                     listOf(CmdBuilder.Operand.IntVal(cmpSlot), CmdBuilder.Operand.LabelRef(endLabel))
                 )
                 val index = compileRefWithFallback(target.indexRef, null, Pos.builtIn) ?: return null
-                builder.emit(Opcode.SET_INDEX, receiver.slot, index.slot, value.slot)
+                if (elementSlotType == SlotType.INT && index.type == SlotType.INT && value.type == SlotType.INT) {
+                    builder.emit(Opcode.SET_INDEX_INT, receiver.slot, index.slot, value.slot)
+                } else {
+                    builder.emit(Opcode.SET_INDEX, receiver.slot, index.slot, value.slot)
+                }
                 noteListElementClassMutation(receiver.slot, value)
                 builder.mark(endLabel)
             }
@@ -3047,13 +3056,12 @@ class BytecodeCompiler(
             val current = allocSlot()
             val result = allocSlot()
             var rhs = compileRef(ref.value) ?: return compileEvalRef(ref)
-            val elementClass = listElementClassBySlot[receiver.slot] ?: listElementClassFromReceiverRef(indexTarget.targetRef)
+            val elementClass = indexElementClass(receiver.slot, indexTarget.targetRef)
             if (!indexTarget.optionalRef) {
                 val index = compileRefWithFallback(indexTarget.indexRef, null, Pos.builtIn) ?: return null
-                if (elementClass == ObjInt.type) {
+                if (elementClass == ObjInt.type && index.type == SlotType.INT) {
-                    builder.emit(Opcode.GET_INDEX, receiver.slot, index.slot, current)
                     val currentInt = allocSlot()
-                    builder.emit(Opcode.UNBOX_INT_OBJ, current, currentInt)
+                    builder.emit(Opcode.GET_INDEX_INT, receiver.slot, index.slot, currentInt)
                     updateSlotType(currentInt, SlotType.INT)
                     if (rhs.type != SlotType.INT) {
                         coerceToArithmeticInt(ref.value, rhs)?.let { rhs = it }
@@ -3067,9 +3075,9 @@ class BytecodeCompiler(
                         else -> null
                     }
                     if (typed != null && typed.type == SlotType.INT) {
-                        builder.emit(Opcode.SET_INDEX, receiver.slot, index.slot, currentInt)
+                        builder.emit(Opcode.SET_INDEX_INT, receiver.slot, index.slot, typed.slot)
                         noteListElementClassMutation(receiver.slot, typed)
-                        return CompiledValue(currentInt, SlotType.INT)
+                        return typed
                     }
                 }
                 builder.emit(Opcode.GET_INDEX, receiver.slot, index.slot, current)
@@ -3321,9 +3329,14 @@ class BytecodeCompiler(
             }
             is IndexRef -> {
                 val receiver = compileRefWithFallback(target.targetRef, null, Pos.builtIn) ?: return null
+                val elementSlotType = indexElementSlotType(receiver.slot, target.targetRef)
                 if (!target.optionalRef) {
                     val index = compileRefWithFallback(target.indexRef, null, Pos.builtIn) ?: return null
-                    builder.emit(Opcode.SET_INDEX, receiver.slot, index.slot, newValue.slot)
+                    if (elementSlotType == SlotType.INT && index.type == SlotType.INT && newValue.type == SlotType.INT) {
+                        builder.emit(Opcode.SET_INDEX_INT, receiver.slot, index.slot, newValue.slot)
+                    } else {
+                        builder.emit(Opcode.SET_INDEX, receiver.slot, index.slot, newValue.slot)
+                    }
                 } else {
                     val recvNull = allocSlot()
                     builder.emit(Opcode.CONST_NULL, recvNull)
@@ -3335,7 +3348,11 @@ class BytecodeCompiler(
                         listOf(CmdBuilder.Operand.IntVal(recvCmp), CmdBuilder.Operand.LabelRef(skipLabel))
                     )
                     val index = compileRefWithFallback(target.indexRef, null, Pos.builtIn) ?: return null
-                    builder.emit(Opcode.SET_INDEX, receiver.slot, index.slot, newValue.slot)
+                    if (elementSlotType == SlotType.INT && index.type == SlotType.INT && newValue.type == SlotType.INT) {
+                        builder.emit(Opcode.SET_INDEX_INT, receiver.slot, index.slot, newValue.slot)
+                    } else {
+                        builder.emit(Opcode.SET_INDEX, receiver.slot, index.slot, newValue.slot)
+                    }
                     builder.mark(skipLabel)
                 }
             }
@@ -3603,9 +3620,15 @@ class BytecodeCompiler(
 
     private fun compileIndexRef(ref: IndexRef): CompiledValue? {
         val receiver = compileRefWithFallback(ref.targetRef, null, Pos.builtIn) ?: return null
+        val elementSlotType = indexElementSlotType(receiver.slot, ref.targetRef)
         val dst = allocSlot()
         if (!ref.optionalRef) {
             val index = compileRefWithFallback(ref.indexRef, null, Pos.builtIn) ?: return null
+            if (elementSlotType == SlotType.INT && index.type == SlotType.INT) {
+                builder.emit(Opcode.GET_INDEX_INT, receiver.slot, index.slot, dst)
+                updateSlotType(dst, SlotType.INT)
+                return CompiledValue(dst, SlotType.INT)
+            }
             builder.emit(Opcode.GET_INDEX, receiver.slot, index.slot, dst)
         } else {
             val nullSlot = allocSlot()
@@ -4234,6 +4257,7 @@ class BytecodeCompiler(
 
         val indexTarget = ref.target as? IndexRef ?: return null
         val receiver = compileRefWithFallback(indexTarget.targetRef, null, Pos.builtIn) ?: return null
+        val elementSlotType = indexElementSlotType(receiver.slot, indexTarget.targetRef)
         if (indexTarget.optionalRef) {
             val resultSlot = allocSlot()
             val nullSlot = allocSlot()
@@ -4273,6 +4297,24 @@ class BytecodeCompiler(
             return CompiledValue(resultSlot, SlotType.OBJ)
         }
         val index = compileRefWithFallback(indexTarget.indexRef, null, Pos.builtIn) ?: return null
+        if (elementSlotType == SlotType.INT && index.type == SlotType.INT) {
+            val current = allocSlot()
+            builder.emit(Opcode.GET_INDEX_INT, receiver.slot, index.slot, current)
+            updateSlotType(current, SlotType.INT)
+            val oneSlot = allocSlot()
+            val oneId = builder.addConst(BytecodeConst.IntVal(1))
+            builder.emit(Opcode.CONST_INT, oneId, oneSlot)
+            updateSlotType(oneSlot, SlotType.INT)
+            val result = allocSlot()
+            val op = if (ref.isIncrement) Opcode.ADD_INT else Opcode.SUB_INT
+            builder.emit(op, current, oneSlot, result)
+            updateSlotType(result, SlotType.INT)
+            builder.emit(Opcode.SET_INDEX_INT, receiver.slot, index.slot, result)
+            if (wantResult && ref.isPost) {
+                return CompiledValue(current, SlotType.INT)
+            }
+            return CompiledValue(result, SlotType.INT)
+        }
         val current = allocSlot()
         builder.emit(Opcode.GET_INDEX, receiver.slot, index.slot, current)
         updateSlotType(current, SlotType.OBJ)
@@ -4636,6 +4678,7 @@ class BytecodeCompiler(
     }
 
     private fun compileMethodCall(ref: MethodCallRef): CompiledValue? {
+        compileListFillIntCall(ref)?.let { return it }
         val callPos = callSitePos()
         val receiverClass = resolveReceiverClass(ref.receiver) ?: ObjDynamic.type
         val receiver = compileRefWithFallback(ref.receiver, null, refPosOrCurrent(ref.receiver)) ?: return null
@@ -4814,6 +4857,22 @@ class BytecodeCompiler(
         return CompiledValue(dst, SlotType.OBJ)
     }
 
+    private fun compileListFillIntCall(ref: MethodCallRef): CompiledValue? {
+        if (ref.name != "fill" || !isListTypeRef(ref.receiver)) return null
+        if (ref.args.size != 2 || ref.args.any { it.isSplat || it.name != null }) return null
+        val lambdaRef = ((ref.args[1].value as? ExpressionStatement)?.ref as? LambdaFnRef) ?: return null
+        if (lambdaRef.inferredReturnClass != ObjInt.type) return null
+        val size = compileArgValue(ref.args[0].value) ?: return null
+        if (size.type != SlotType.INT) return null
+        val callable = ensureObjSlot(compileArgValue(ref.args[1].value) ?: return null)
+        val dst = allocSlot()
+        builder.emit(Opcode.LIST_FILL_INT, size.slot, callable.slot, dst)
+        updateSlotType(dst, SlotType.OBJ)
+        slotObjClass[dst] = ObjList.type
+        listElementClassBySlot[dst] = ObjInt.type
+        return CompiledValue(dst, SlotType.OBJ)
+    }
+
     private fun compileThisMethodSlotCall(ref: ThisMethodSlotCallRef): CompiledValue? {
         val callPos = callSitePos()
         val receiver = compileThisRef()
@@ -6119,6 +6178,42 @@ class BytecodeCompiler(
         }
         return when (directRef) {
             is ListLiteralRef -> listElementClassFromListLiteralRef(directRef)
+            is MethodCallRef -> listElementClassFromMethodCallRef(directRef)
+            else -> null
+        }
+    }
+
+    private fun listElementClassFromMethodCallRef(ref: MethodCallRef): ObjClass? {
+        if (ref.name != "fill" || !isListTypeRef(ref.receiver)) return null
+        val block = ref.args.lastOrNull() ?: return null
+        return supportedListElementClass(listElementClassFromFillValue(block.value))
+    }
+
+    private fun listElementClassFromFillValue(value: Obj): ObjClass? {
+        val expr = value as? ExpressionStatement ?: return null
+        val ref = when (val directRef = expr.ref) {
+            is StatementRef -> (directRef.statement as? ExpressionStatement)?.ref
+            else -> directRef
+        } ?: return null
+        return when (ref) {
+            is ConstRef -> elementClassFromConst(ref.constValue)
+            is LambdaFnRef -> ref.inferredReturnClass
+            else -> null
+        }
+    }
+
+    private fun isListTypeRef(ref: ObjRef): Boolean {
+        return when (ref) {
+            is LocalVarRef -> ref.name == "List"
+            is LocalSlotRef -> ref.name == "List"
+            is FastLocalVarRef -> ref.name == "List"
+            else -> false
+        }
+    }
+
+    private fun supportedListElementClass(cls: ObjClass?): ObjClass? {
+        return when (cls) {
+            ObjInt.type, ObjReal.type, ObjString.type, ObjBool.type -> cls
             else -> null
         }
     }
@@ -7774,6 +7869,12 @@ class BytecodeCompiler(
         }
     }
 
+    private fun indexElementClass(receiverSlot: Int, targetRef: ObjRef): ObjClass? =
+        listElementClassBySlot[receiverSlot] ?: listElementClassFromReceiverRef(targetRef)
+
+    private fun indexElementSlotType(receiverSlot: Int, targetRef: ObjRef): SlotType? =
+        slotTypeFromClass(indexElementClass(receiverSlot, targetRef))
+
     private fun prepareCompilation(stmt: Statement) {
         builder = CmdBuilder()
         nextSlot = 0
@@ -8860,31 +8961,14 @@ class BytecodeCompiler(
             SlotType.OBJ -> {
                 val isExactInt = isExactNonNullSlotClassOrTemp(value.slot, ObjInt.type)
                 val isStableIntObj = slotObjClass[value.slot] == ObjInt.type && isStablePrimitiveSourceSlot(value.slot)
-                if (!isExactInt && !isStableIntObj && !isStablePrimitiveSourceSlot(value.slot)) return null
+                if (!isExactInt && !isStableIntObj) return null
-                val objSlot = if (isExactInt || isStableIntObj) {
+                val objSlot = value.slot
-                    value.slot
-                } else {
-                    val boxed = allocSlot()
-                    builder.emit(Opcode.BOX_OBJ, value.slot, boxed)
-                    updateSlotType(boxed, SlotType.OBJ)
-                    emitAssertObjSlotIsInt(boxed)
-                }
                 val intSlot = allocSlot()
                 builder.emit(Opcode.UNBOX_INT_OBJ, objSlot, intSlot)
                 updateSlotType(intSlot, SlotType.INT)
                 CompiledValue(intSlot, SlotType.INT)
             }
-            SlotType.UNKNOWN -> {
+            SlotType.UNKNOWN -> null
-                if (!isStablePrimitiveSourceSlot(value.slot)) return null
-                val boxed = allocSlot()
-                builder.emit(Opcode.BOX_OBJ, value.slot, boxed)
-                updateSlotType(boxed, SlotType.OBJ)
-                val checked = emitAssertObjSlotIsInt(boxed)
-                val intSlot = allocSlot()
-                builder.emit(Opcode.UNBOX_INT_OBJ, checked, intSlot)
-                updateSlotType(intSlot, SlotType.INT)
-                CompiledValue(intSlot, SlotType.INT)
-            }
             else -> null
         }
     }
@@ -8980,12 +9064,7 @@ class BytecodeCompiler(
     }
 
     private fun extractTypedRangeLocal(source: Statement): LocalSlotRef? {
-        if (rangeLocalNames.isEmpty()) return null
+        return null
-        val target = if (source is BytecodeStatement) source.original else source
-        val expr = target as? ExpressionStatement ?: return null
-        val localRef = expr.ref as? LocalSlotRef ?: return null
-        if (localRef.isDelegated) return null
-        return if (rangeLocalNames.contains(localRef.name)) localRef else null
     }
 
     private data class ScopeSlotKey(val scopeId: Int, val slot: Int)

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bytecode/CmdBuilder.kt

@@ -227,6 +227,12 @@ class CmdBuilder {
                 listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
             Opcode.SET_INDEX ->
                 listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
+            Opcode.GET_INDEX_INT ->
+                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
+            Opcode.SET_INDEX_INT ->
+                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
+            Opcode.LIST_FILL_INT ->
+                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
             Opcode.MAKE_RANGE ->
                 listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
             Opcode.LIST_LITERAL ->
@@ -827,6 +833,9 @@ class CmdBuilder {
             Opcode.CALL_DYNAMIC_MEMBER -> CmdCallDynamicMember(operands[0], operands[1], operands[2], operands[3], operands[4])
             Opcode.GET_INDEX -> CmdGetIndex(operands[0], operands[1], operands[2])
             Opcode.SET_INDEX -> CmdSetIndex(operands[0], operands[1], operands[2])
+            Opcode.GET_INDEX_INT -> CmdGetIndexInt(operands[0], operands[1], operands[2])
+            Opcode.SET_INDEX_INT -> CmdSetIndexInt(operands[0], operands[1], operands[2])
+            Opcode.LIST_FILL_INT -> CmdListFillInt(operands[0], operands[1], operands[2])
             Opcode.LIST_LITERAL -> CmdListLiteral(operands[0], operands[1], operands[2], operands[3])
             Opcode.GET_MEMBER_SLOT -> CmdGetMemberSlot(operands[0], operands[1], operands[2], operands[3])
             Opcode.SET_MEMBER_SLOT -> CmdSetMemberSlot(operands[0], operands[1], operands[2], operands[3])

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bytecode/CmdDisassembler.kt

@@ -493,6 +493,9 @@ object CmdDisassembler {
             is CmdCallDynamicMember -> Opcode.CALL_DYNAMIC_MEMBER to intArrayOf(cmd.recvSlot, cmd.nameId, cmd.argBase, cmd.argCount, cmd.dst)
             is CmdGetIndex -> Opcode.GET_INDEX to intArrayOf(cmd.targetSlot, cmd.indexSlot, cmd.dst)
             is CmdSetIndex -> Opcode.SET_INDEX to intArrayOf(cmd.targetSlot, cmd.indexSlot, cmd.valueSlot)
+            is CmdGetIndexInt -> Opcode.GET_INDEX_INT to intArrayOf(cmd.targetSlot, cmd.indexSlot, cmd.dst)
+            is CmdSetIndexInt -> Opcode.SET_INDEX_INT to intArrayOf(cmd.targetSlot, cmd.indexSlot, cmd.valueSlot)
+            is CmdListFillInt -> Opcode.LIST_FILL_INT to intArrayOf(cmd.sizeSlot, cmd.callableSlot, cmd.dst)
             is CmdListLiteral -> Opcode.LIST_LITERAL to intArrayOf(cmd.planId, cmd.baseSlot, cmd.count, cmd.dst)
             is CmdGetMemberSlot -> Opcode.GET_MEMBER_SLOT to intArrayOf(cmd.recvSlot, cmd.fieldId, cmd.methodId, cmd.dst)
             is CmdSetMemberSlot -> Opcode.SET_MEMBER_SLOT to intArrayOf(cmd.recvSlot, cmd.fieldId, cmd.methodId, cmd.valueSlot)
@@ -612,6 +615,12 @@ object CmdDisassembler {
                 listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
             Opcode.SET_INDEX ->
                 listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
+            Opcode.GET_INDEX_INT ->
+                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
+            Opcode.SET_INDEX_INT ->
+                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
+            Opcode.LIST_FILL_INT ->
+                listOf(OperandKind.SLOT, OperandKind.SLOT, OperandKind.SLOT)
             Opcode.LIST_LITERAL ->
                 listOf(OperandKind.CONST, OperandKind.SLOT, OperandKind.COUNT, OperandKind.SLOT)
             Opcode.GET_MEMBER_SLOT ->

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bytecode/CmdRuntime.kt

@@ -3352,6 +3352,31 @@ class CmdListLiteral(
     }
 }
 
+class CmdListFillInt(
+    internal val sizeSlot: Int,
+    internal val callableSlot: Int,
+    internal val dst: Int,
+) : Cmd() {
+    override suspend fun perform(frame: CmdFrame) {
+        val size = frame.getInt(sizeSlot).toInt()
+        if (size < 0) frame.ensureScope().raiseIllegalArgument("list size must be non-negative")
+        val callable = frame.storedSlotObj(callableSlot)
+        val scope = frame.ensureScope()
+        val result = ObjList(LongArray(size))
+        for (i in 0 until size) {
+            val value = if (callable is BytecodeLambdaCallable && callable.supportsImplicitIntFillFastPath()) {
+                callable.invokeImplicitIntArg(scope, i.toLong())
+            } else {
+                callable.callOn(scope.createChildScope(scope.pos, args = Arguments(ObjInt.of(i.toLong()))))
+            }
+            val intValue = (value as? ObjInt)?.value ?: scope.raiseClassCastError("expected Int fill result")
+            result.setIntAtFast(i, intValue)
+        }
+        frame.storeObjResult(dst, result)
+        return
+    }
+}
+
 private fun decodeMemberId(id: Int): Pair<Int, Boolean> {
     return if (id <= -2) {
         Pair(-id - 2, true)
@@ -3709,7 +3734,7 @@ class CmdGetIndex(
         val target = frame.storedSlotObj(targetSlot)
         val index = frame.storedSlotObj(indexSlot)
         if (target is ObjList && target::class == ObjList::class && index is ObjInt) {
-            frame.storeObjResult(dst, target.list[index.toInt()])
+            frame.storeObjResult(dst, target.getObjAtFast(index.toInt()))
             return
         }
         val result = target.getAt(frame.ensureScope(), index)
@@ -3728,7 +3753,7 @@ class CmdSetIndex(
         val index = frame.storedSlotObj(indexSlot)
         val value = frame.slotToObj(valueSlot)
         if (target is ObjList && target::class == ObjList::class && index is ObjInt) {
-            target.list[index.toInt()] = value
+            target.setObjAtFast(index.toInt(), value)
             return
         }
         target.putAt(frame.ensureScope(), index, value)
@@ -3736,6 +3761,47 @@ class CmdSetIndex(
     }
 }
 
+class CmdGetIndexInt(
+    internal val targetSlot: Int,
+    internal val indexSlot: Int,
+    internal val dst: Int,
+) : Cmd() {
+    override suspend fun perform(frame: CmdFrame) {
+        val target = frame.storedSlotObj(targetSlot)
+        val index = frame.getInt(indexSlot).toInt()
+        if (target is ObjList && target::class == ObjList::class) {
+            target.getIntAtFast(index)?.let {
+                frame.setInt(dst, it)
+                return
+            }
+        }
+        val result = target.getAt(frame.ensureScope(), ObjInt.of(index.toLong()))
+        if (result is ObjInt) {
+            frame.setInt(dst, result.value)
+            return
+        }
+        frame.ensureScope().raiseClassCastError("expected Int list element")
+    }
+}
+
+class CmdSetIndexInt(
+    internal val targetSlot: Int,
+    internal val indexSlot: Int,
+    internal val valueSlot: Int,
+) : Cmd() {
+    override suspend fun perform(frame: CmdFrame) {
+        val target = frame.storedSlotObj(targetSlot)
+        val index = frame.getInt(indexSlot).toInt()
+        if (target is ObjList && target::class == ObjList::class) {
+            target.setIntAtFast(index, frame.getInt(valueSlot))
+            return
+        }
+        val value = ObjInt.of(frame.getInt(valueSlot))
+        target.putAt(frame.ensureScope(), ObjInt.of(index.toLong()), value)
+        return
+    }
+}
+
 class CmdMakeLambda(internal val id: Int, internal val dst: Int) : Cmd() {
     override suspend fun perform(frame: CmdFrame) {
         val lambdaConst = frame.fn.constants.getOrNull(id) as? BytecodeConst.LambdaFn
@@ -3788,6 +3854,31 @@ class BytecodeLambdaCallable(
         )
     }
 
+    fun supportsImplicitIntFillFastPath(): Boolean = argsDeclaration == null
+
+    suspend fun invokeImplicitIntArg(scope: Scope, arg: Long): Obj {
+        val context = scope.applyClosureForBytecode(closureScope, preferredThisType).also {
+            it.args = Arguments.EMPTY
+        }
+        if (captureRecords != null) {
+            context.captureRecords = captureRecords
+            context.captureNames = captureNames
+        } else if (captureNames.isNotEmpty()) {
+            closureScope.raiseIllegalState("bytecode lambda capture records missing")
+        }
+        val binder: suspend (CmdFrame, Arguments) -> Unit = { frame, _ ->
+            paramSlotPlan["it"]?.let { itSlot ->
+                frame.frame.setInt(itSlot, arg)
+            }
+        }
+        return try {
+            CmdVm().execute(fn, context, Arguments.EMPTY, binder)
+        } catch (e: ReturnException) {
+            if (e.label == null || returnLabels.contains(e.label)) e.result
+            else throw e
+        }
+    }
+
     override suspend fun execute(scope: Scope): Obj {
         val context = scope.applyClosureForBytecode(closureScope, preferredThisType).also {
             it.args = scope.args
@@ -3818,7 +3909,12 @@ class BytecodeLambdaCallable(
                     }
                     val itSlot = slotPlan["it"]
                     if (itSlot != null) {
-                        frame.frame.setObj(itSlot, itValue)
+                        when (itValue) {
+                            is ObjInt -> frame.frame.setInt(itSlot, itValue.value)
+                            is ObjReal -> frame.frame.setReal(itSlot, itValue.value)
+                            is ObjBool -> frame.frame.setBool(itSlot, itValue.value)
+                            else -> frame.frame.setObj(itSlot, itValue)
+                        }
                     }
                 } else {
                     argsDeclaration.assignToFrame(

lynglib/src/commonMain/kotlin/net/sergeych/lyng/bytecode/Opcode.kt

@@ -177,7 +177,10 @@ enum class Opcode(val code: Int) {
 
     GET_INDEX(0xA2),
     SET_INDEX(0xA3),
+    GET_INDEX_INT(0xA4),
     LIST_LITERAL(0xA5),
+    SET_INDEX_INT(0xA6),
+    LIST_FILL_INT(0xA7),
     GET_MEMBER_SLOT(0xA8),
     SET_MEMBER_SLOT(0xA9),
     GET_CLASS_SCOPE(0xAA),

lynglib/src/commonMain/kotlin/net/sergeych/lyng/obj/LambdaFnRef.kt

@@ -12,6 +12,7 @@
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
+ *
  */
 
 package net.sergeych.lyng.obj
@@ -28,6 +29,7 @@ class LambdaFnRef(
     val paramSlotPlan: Map<String, Int>,
     val argsDeclaration: ArgsDeclaration?,
     val captureEntries: List<LambdaCaptureEntry>,
+    val inferredReturnClass: ObjClass?,
     val preferredThisType: String?,
     val wrapAsExtensionCallable: Boolean,
     val returnLabels: Set<String>,

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

@@ -19,8 +19,8 @@ package net.sergeych.lyng.obj
 
 import kotlinx.serialization.json.JsonArray
 import kotlinx.serialization.json.JsonElement
-import net.sergeych.lyng.Scope
 import net.sergeych.lyng.Arguments
+import net.sergeych.lyng.Scope
 import net.sergeych.lyng.miniast.ParamDoc
 import net.sergeych.lyng.miniast.addFnDoc
 import net.sergeych.lyng.miniast.addPropertyDoc
@@ -29,7 +29,120 @@ import net.sergeych.lynon.LynonDecoder
 import net.sergeych.lynon.LynonEncoder
 import net.sergeych.lynon.LynonType
 
-open class ObjList(val list: MutableList<Obj> = mutableListOf()) : Obj() {
+open class ObjList(initialList: MutableList<Obj> = mutableListOf()) : Obj() {
+    private var boxedList: MutableList<Obj>? = null
+    private var primitiveIntList: LongArray? = null
+
+    init {
+        if (!adoptPrimitiveIntList(initialList)) {
+            boxedList = initialList
+        }
+    }
+
+    val list: MutableList<Obj>
+        get() = ensureBoxedList()
+
+    internal fun sizeFast(): Int = primitiveIntList?.size ?: boxedList?.size ?: 0
+
+    internal fun getObjAtFast(index: Int): Obj =
+        primitiveIntList?.let { ObjInt.of(it[index]) } ?: boxedList!![index]
+
+    internal fun getIntAtFast(index: Int): Long? =
+        primitiveIntList?.get(index) ?: (boxedList?.get(index) as? ObjInt)?.value
+
+    internal fun setObjAtFast(index: Int, value: Obj) {
+        val ints = primitiveIntList
+        if (ints != null) {
+            if (value is ObjInt) {
+                ints[index] = value.value
+                return
+            }
+            ensureBoxedList()[index] = value
+            return
+        }
+        boxedList!![index] = value
+    }
+
+    internal fun setIntAtFast(index: Int, value: Long) {
+        val ints = primitiveIntList
+        if (ints != null) {
+            ints[index] = value
+            return
+        }
+        boxedList?.let {
+            if (it[index] is ObjInt) {
+                it[index] = ObjInt.of(value)
+                return
+            }
+        }
+        ensureBoxedList()[index] = ObjInt.of(value)
+    }
+
+    internal fun appendFast(value: Obj) {
+        val ints = primitiveIntList
+        if (ints != null && value is ObjInt) {
+            primitiveIntList = ints.copyOf(ints.size + 1).also { it[ints.size] = value.value }
+            return
+        }
+        ensureBoxedList().add(value)
+    }
+
+    internal fun appendAllFast(other: ObjList) {
+        val ints = primitiveIntList
+        val otherInts = other.primitiveIntList
+        if (ints != null && otherInts != null) {
+            primitiveIntList = LongArray(ints.size + otherInts.size).also {
+                ints.copyInto(it, 0, 0, ints.size)
+                otherInts.copyInto(it, ints.size, 0, otherInts.size)
+            }
+            return
+        }
+        ensureBoxedList().addAll(other.list)
+    }
+
+    private fun adoptPrimitiveIntList(items: List<Obj>): Boolean {
+        if (items.isEmpty()) return false
+        val ints = LongArray(items.size)
+        for (i in items.indices) {
+            val value = items[i] as? ObjInt ?: return false
+            ints[i] = value.value
+        }
+        primitiveIntList = ints
+        boxedList = null
+        return true
+    }
+
+    private fun ensureBoxedList(): MutableList<Obj> {
+        boxedList?.let { return it }
+        val ints = primitiveIntList
+        if (ints == null) {
+            val empty = mutableListOf<Obj>()
+            boxedList = empty
+            return empty
+        }
+        val materialized = ArrayList<Obj>(ints.size)
+        for (value in ints) {
+            materialized.add(ObjInt.of(value))
+        }
+        boxedList = materialized
+        primitiveIntList = null
+        return materialized
+    }
+
+    private fun sliceRange(start: Int, endExclusive: Int): Obj {
+        val ints = primitiveIntList
+        return if (ints != null) {
+            ObjList(ints.copyOfRange(start, endExclusive))
+        } else {
+            ObjList(list.subList(start, endExclusive).toMutableList())
+        }
+    }
+
+    internal constructor(intValues: LongArray) : this(mutableListOf()) {
+        primitiveIntList = intValues
+        boxedList = null
+    }
+
     protected open fun shouldTreatAsSingleElement(scope: Scope, other: Obj): Boolean {
         if (!other.isInstanceOf(ObjIterable)) return true
         val declaredElementType = scope.declaredListElementTypeForValue(this)
@@ -48,9 +161,9 @@ open class ObjList(val list: MutableList<Obj> = mutableListOf()) : Obj() {
             }
             return false
         }
-        if (list.size != other.list.size) return false
+        if (sizeFast() != other.sizeFast()) return false
-        for (i in 0..<list.size) {
+        for (i in 0..<sizeFast()) {
-            if (!list[i].equals(scope, other.list[i])) return false
+            if (!getObjAtFast(i).equals(scope, other.getObjAtFast(i))) return false
         }
         return true
     }
@@ -58,31 +171,31 @@ open class ObjList(val list: MutableList<Obj> = mutableListOf()) : Obj() {
     override suspend fun getAt(scope: Scope, index: Obj): Obj {
         return when (index) {
             is ObjInt -> {
-                list[index.toInt()]
+                getObjAtFast(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())
+                            sliceRange(index.start.toInt(), index.end.toInt() + 1)
                         else
-                            ObjList(list.subList(index.start.toInt(), index.end.toInt()).toMutableList())
+                            sliceRange(index.start.toInt(), index.end.toInt())
                     }
 
                     index.isOpenStart && !index.isOpenEnd -> {
                         if (index.isEndInclusive)
-                            ObjList(list.subList(0, index.end!!.toInt() + 1).toMutableList())
+                            sliceRange(0, index.end!!.toInt() + 1)
                         else
-                            ObjList(list.subList(0, index.end!!.toInt()).toMutableList())
+                            sliceRange(0, index.end!!.toInt())
                     }
 
                     index.isOpenEnd && !index.isOpenStart -> {
-                        ObjList(list.subList(index.start!!.toInt(), list.size).toMutableList())
+                        sliceRange(index.start!!.toInt(), sizeFast())
                     }
 
                     index.isOpenStart && index.isOpenEnd -> {
-                        ObjList(list.toMutableList())
+                        sliceRange(0, sizeFast())
                     }
 
                     else -> {
@@ -96,16 +209,16 @@ open class ObjList(val list: MutableList<Obj> = mutableListOf()) : Obj() {
     }
 
     open override suspend fun putAt(scope: Scope, index: Obj, newValue: Obj) {
-        list[index.toInt()] = newValue
+        setObjAtFast(index.toInt(), newValue)
     }
 
     override suspend fun compareTo(scope: Scope, other: Obj): Int {
         if (other is ObjList) {
-            val mySize = list.size
+            val mySize = sizeFast()
-            val otherSize = other.list.size
+            val otherSize = other.sizeFast()
             val commonSize = minOf(mySize, otherSize)
             for (i in 0..<commonSize) {
-                val d = list[i].compareTo(scope, other.list[i])
+                val d = getObjAtFast(i).compareTo(scope, other.getObjAtFast(i))
                 if (d != 0) {
                     return d
                 }
@@ -114,14 +227,13 @@ open class ObjList(val list: MutableList<Obj> = mutableListOf()) : Obj() {
             return res
         }
         if (other.isInstanceOf(ObjIterable)) {
-            val it1 = this.list.iterator()
             val it2 = other.invokeInstanceMethod(scope, "iterator")
             val hasNext2 = it2.getInstanceMethod(scope, "hasNext")
             val next2 = it2.getInstanceMethod(scope, "next")
-            
+
-            while (it1.hasNext()) {
+            for (i in 0..<sizeFast()) {
                 if (!hasNext2.invoke(scope, it2).toBool()) return 1 // I'm longer
-                val v1 = it1.next()
+                val v1 = getObjAtFast(i)
                 val v2 = next2.invoke(scope, it2)
                 val d = v1.compareTo(scope, v2)
                 if (d != 0) return d
@@ -133,8 +245,18 @@ open class ObjList(val list: MutableList<Obj> = mutableListOf()) : Obj() {
 
     override suspend fun plus(scope: Scope, other: Obj): Obj =
         when {
-            other is ObjList ->
+            other is ObjList -> {
-                ObjList((list + other.list).toMutableList())
+                val ints = primitiveIntList
+                val otherInts = other.primitiveIntList
+                if (ints != null && otherInts != null) {
+                    ObjList(LongArray(ints.size + otherInts.size).also {
+                        ints.copyInto(it, 0, 0, ints.size)
+                        otherInts.copyInto(it, ints.size, 0, otherInts.size)
+                    })
+                } else {
+                    ObjList((list + other.list).toMutableList())
+                }
+            }
 
             !shouldTreatAsSingleElement(scope, other) && other.isInstanceOf(ObjIterable) -> {
                 val l = other.callMethod<ObjList>(scope, "toList")
@@ -151,12 +273,12 @@ open class ObjList(val list: MutableList<Obj> = mutableListOf()) : Obj() {
 
     open override suspend fun plusAssign(scope: Scope, other: Obj): Obj {
         if (other is ObjList) {
-            list.addAll(other.list)
+            appendAllFast(other)
         } else if (!shouldTreatAsSingleElement(scope, other) && other.isInstanceOf(ObjIterable)) {
             val otherList = (other.invokeInstanceMethod(scope, "toList") as ObjList).list
             list.addAll(otherList)
         } else {
-            list.add(other)
+            appendFast(other)
         }
         return this
     }
@@ -199,6 +321,13 @@ open class ObjList(val list: MutableList<Obj> = mutableListOf()) : Obj() {
     }
 
     override suspend fun contains(scope: Scope, other: Obj): Boolean {
+        val ints = primitiveIntList
+        if (ints != null && other is ObjInt) {
+            for (value in ints) {
+                if (value == other.value) return true
+            }
+            return false
+        }
         if (net.sergeych.lyng.PerfFlags.PRIMITIVE_FASTOPS) {
             // Fast path: int membership in a list of ints (common case in benches)
             if (other is ObjInt) {
@@ -216,6 +345,13 @@ open class ObjList(val list: MutableList<Obj> = mutableListOf()) : Obj() {
     }
 
     override suspend fun enumerate(scope: Scope, callback: suspend (Obj) -> Boolean) {
+        val ints = primitiveIntList
+        if (ints != null) {
+            for (value in ints) {
+                if (!callback(ObjInt.of(value))) break
+            }
+            return
+        }
         for (item in list) {
             if (!callback(item)) break
         }
@@ -225,6 +361,8 @@ open class ObjList(val list: MutableList<Obj> = mutableListOf()) : Obj() {
         get() = type
 
     override suspend fun toKotlin(scope: Scope): Any {
+        val ints = primitiveIntList
+        if (ints != null) return ints.map { it }
         return list.map { it.toKotlin(scope) }
     }
 
@@ -256,8 +394,7 @@ open class ObjList(val list: MutableList<Obj> = mutableListOf()) : Obj() {
     }
 
     override fun hashCode(): Int {
-        // check?
+        return primitiveIntList?.contentHashCode() ?: list.hashCode()
-        return list.hashCode()
     }
 
     override fun equals(other: Any?): Boolean {
@@ -266,16 +403,31 @@ open class ObjList(val list: MutableList<Obj> = mutableListOf()) : Obj() {
 
         other as ObjList
 
-        return list == other.list
+        val ints = primitiveIntList
+        val otherInts = other.primitiveIntList
+        return if (ints != null && otherInts != null) {
+            ints.contentEquals(otherInts)
+        } else {
+            list == other.list
+        }
     }
 
     override suspend fun serialize(scope: Scope, encoder: LynonEncoder, lynonType: LynonType?) {
-        encoder.encodeAnyList(scope,list)
+        val ints = primitiveIntList
+        if (ints != null) {
+            encoder.encodeAnyList(scope, ints.mapTo(ArrayList(ints.size)) { ObjInt.of(it) })
+            return
+        }
+        encoder.encodeAnyList(scope, list)
     }
 
     override suspend fun lynonType(): LynonType = LynonType.List
 
     override suspend fun toJson(scope: Scope): JsonElement {
+        val ints = primitiveIntList
+        if (ints != null) {
+            return JsonArray(ints.map { ObjInt.of(it).toJson(scope) })
+        }
         return JsonArray(list.map { it.toJson(scope) })
     }
 
@@ -283,9 +435,17 @@ open class ObjList(val list: MutableList<Obj> = mutableListOf()) : Obj() {
         return ObjString(buildString {
             append("[")
             var first = true
-            for (v in list) {
+            val ints = primitiveIntList
-                if (first) first = false else append(",")
+            if (ints != null) {
-                append(v.toString(scope).value)
+                for (v in ints) {
+                    if (first) first = false else append(",")
+                    append(v)
+                }
+            } else {
+                for (v in list) {
+                    if (first) first = false else append(",")
+                    append(v.toString(scope).value)
+                }
             }
             append("]")
         })
@@ -307,7 +467,7 @@ open class ObjList(val list: MutableList<Obj> = mutableListOf()) : Obj() {
                 type = type("lyng.Int"),
                 moduleName = "lyng.stdlib",
                 getter = { 
-                    val s = (this.thisObj as ObjList).list.size
+                    val s = (this.thisObj as ObjList).sizeFast()
                     s.toObj()
                 }
             )

lynglib/src/commonTest/kotlin/BytecodeRecentOpsTest.kt

@@ -16,21 +16,11 @@
  */
 
 import kotlinx.coroutines.test.runTest
-import net.sergeych.lyng.Compiler
+import net.sergeych.lyng.*
-import net.sergeych.lyng.ExecutionError
-import net.sergeych.lyng.Pos
-import net.sergeych.lyng.Script
-import net.sergeych.lyng.ScriptError
-import net.sergeych.lyng.Source
-import net.sergeych.lyng.eval
-import net.sergeych.lyng.toSource
-import net.sergeych.lyng.bytecode.CmdDisassembler
-import net.sergeych.lyng.bytecode.CmdFunction
 import net.sergeych.lyng.obj.toInt
 import kotlin.test.Test
 import kotlin.test.assertEquals
 import kotlin.test.assertFailsWith
-import kotlin.test.assertNotNull
 import kotlin.test.assertTrue
 
 class BytecodeRecentOpsTest {
@@ -129,6 +119,79 @@ class BytecodeRecentOpsTest {
         )
     }
 
+    @Test
+    fun intListIndexOpsUsePrimitiveBytecode() = runTest {
+        val scope = Script.newScope()
+        scope.eval(
+            """
+            fun calc() {
+                var a: List<Int> = [1, 2, 3]
+                val s = a[1]
+                a[1] += 3
+                a[1]++
+                a[1] = s
+                a[1]
+            }
+            """.trimIndent()
+        )
+        val disasm = scope.disassembleSymbol("calc")
+        assertTrue(disasm.contains("GET_INDEX_INT"), disasm)
+        assertTrue(disasm.contains("SET_INDEX_INT"), disasm)
+        assertEquals(2, scope.eval("calc()").toInt())
+    }
+
+    @Test
+    fun listFillIntIndexOpsUsePrimitiveBytecode() = runTest {
+        val scope = Script.newScope()
+        scope.eval(
+            """
+            fun calc() {
+                var a = List.fill(4) { 2 }
+                val s = a[1]
+                a[1] += 3
+                a[1] = s
+                a[1]
+            }
+            """.trimIndent()
+        )
+        val disasm = scope.disassembleSymbol("calc")
+        assertTrue(disasm.contains("GET_INDEX_INT"), disasm)
+        assertTrue(disasm.contains("SET_INDEX_INT"), disasm)
+        assertEquals(2, scope.eval("calc()").toInt())
+    }
+
+    @Test
+    fun listFillIntUsesPrimitiveFillBytecode() = runTest {
+        val scope = Script.newScope()
+        scope.eval(
+            """
+            fun calc() {
+                val xs = List.fill(5) { 2 }
+                xs[0] + xs[4]
+            }
+            """.trimIndent()
+        )
+        val disasm = scope.disassembleSymbol("calc")
+        assertTrue(disasm.contains("LIST_FILL_INT"), disasm)
+        assertEquals(4, scope.eval("calc()").toInt())
+    }
+
+    @Test
+    fun listFillIntWithIndexLambdaKeepsSemantics() = runTest {
+        val scope = Script.newScope()
+        scope.eval(
+            """
+            fun calc() {
+                val xs = List.fill(5) { it * 3 }
+                xs[0] + xs[4]
+            }
+            """.trimIndent()
+        )
+        val disasm = scope.disassembleSymbol("calc")
+        assertTrue(disasm.contains("LIST_FILL_INT"), disasm)
+        assertEquals(12, scope.eval("calc()").toInt())
+    }
+
     @Test
     fun optionalIndexPreIncSkipsOnNullReceiver() = runTest {
         eval(

lynglib/src/commonTest/kotlin/CoroutinesTest.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2025 Sergey S. Chernov real.sergeych@gmail.com
+ * Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -97,7 +97,7 @@ class TestCoroutines {
                         counter = c + 1
 //                    }
                 }
-             }.forEach { (it as Deferred).await() }
+             }.forEach { it.await() }
              println(counter)
              assert( counter < 10 )
              
@@ -105,6 +105,21 @@ class TestCoroutines {
         )
     }
 
+    @Test
+    fun testMapForEachDeferredInference() = runTest {
+        eval(
+            """
+            var sum = 0
+
+            (1..3).map { n ->
+                launch { n }
+            }.forEach { sum += it.await() }
+
+            assertEquals(6, sum)
+            """.trimIndent()
+        )
+    }
+
     @Test
     fun testFlows() = runTest {
         eval("""

lynglib/src/jvmTest/kotlin/PiSpigotBenchmarkTest.kt

@@ -16,25 +16,13 @@
  */
 
 import kotlinx.coroutines.test.runTest
-import net.sergeych.lyng.Benchmarks
+import net.sergeych.lyng.*
-import net.sergeych.lyng.BytecodeBodyProvider
+import net.sergeych.lyng.bytecode.*
-import net.sergeych.lyng.PerfFlags
-import net.sergeych.lyng.PerfProfiles
-import net.sergeych.lyng.Script
-import net.sergeych.lyng.Statement
-import net.sergeych.lyng.bytecode.BytecodeStatement
-import net.sergeych.lyng.bytecode.CmdCallMemberSlot
-import net.sergeych.lyng.bytecode.CmdFunction
-import net.sergeych.lyng.bytecode.CmdGetIndex
-import net.sergeych.lyng.bytecode.CmdIterPush
-import net.sergeych.lyng.bytecode.CmdMakeRange
-import net.sergeych.lyng.bytecode.CmdSetIndex
 import net.sergeych.lyng.obj.ObjString
 import java.nio.file.Files
 import java.nio.file.Path
 import kotlin.test.Test
 import kotlin.test.assertEquals
-import kotlin.test.assertTrue
 import kotlin.time.TimeSource
 
 class PiSpigotBenchmarkTest {
@@ -42,17 +30,11 @@ class PiSpigotBenchmarkTest {
     fun benchmarkPiSpigot() = runTest {
         if (!Benchmarks.enabled) return@runTest
 
-        val source = Files.readString(resolveExample("pi-test.lyng"))
+        val source = loadPiSpigotSource()
-        val legacySource = source.replace(
-            "val quotient = sum / denom",
-            "var quotient = floor((sum / (denom * 1.0))).toInt()"
-        )
-        assertTrue(legacySource != source, "failed to build legacy piSpigot benchmark case")
 
         val digits = 200
         val expectedSuffix = "49303819"
 
-        val legacyElapsed = runCase("legacy-real-division", legacySource, digits, expectedSuffix, dumpBytecode = true)
         val saved = PerfProfiles.snapshot()
         PerfFlags.RVAL_FASTPATH = false
         val optimizedRvalOffElapsed = runCase(
@@ -64,15 +46,11 @@ class PiSpigotBenchmarkTest {
         )
         PerfProfiles.restore(saved)
         val optimizedElapsed = runCase("optimized-int-division-rval-on", source, digits, expectedSuffix, dumpBytecode = true)
-        val sourceSpeedup = legacyElapsed.toDouble() / optimizedRvalOffElapsed.toDouble()
         val runtimeSpeedup = optimizedRvalOffElapsed.toDouble() / optimizedElapsed.toDouble()
-        val totalSpeedup = legacyElapsed.toDouble() / optimizedElapsed.toDouble()
         println(
-            "[DEBUG_LOG] [BENCH] pi-spigot compare n=$digits legacy=${legacyElapsed} ms " +
+            "[DEBUG_LOG] [BENCH] pi-spigot compare n=$digits " +
-                "intDiv=${optimizedRvalOffElapsed} ms rvalOn=${optimizedElapsed} ms " +
+                "rvalOff=${optimizedRvalOffElapsed} ms rvalOn=${optimizedElapsed} ms " +
-                "intDivSpeedup=${"%.2f".format(sourceSpeedup)}x " +
+                "rvalSpeedup=${"%.2f".format(runtimeSpeedup)}x"
-                "rvalSpeedup=${"%.2f".format(runtimeSpeedup)}x " +
-                "total=${"%.2f".format(totalSpeedup)}x"
         )
     }
 
@@ -91,18 +69,18 @@ class PiSpigotBenchmarkTest {
             dumpHotOps(scope, "piSpigot")
         }
 
-        val first = scope.eval("piSpigot($digits)") as ObjString
+        val first = scope.eval("piSpigot(0, $digits)") as ObjString
         assertEquals(expectedSuffix, first.value)
 
         repeat(2) {
-            val warm = scope.eval("piSpigot($digits)") as ObjString
+            val warm = scope.eval("piSpigot(0, $digits)") as ObjString
             assertEquals(expectedSuffix, warm.value)
         }
 
         val iterations = 3
         val start = TimeSource.Monotonic.markNow()
         repeat(iterations) {
-            val result = scope.eval("piSpigot($digits)") as ObjString
+            val result = scope.eval("piSpigot(0, $digits)") as ObjString
             assertEquals(expectedSuffix, result.value)
         }
         val elapsedMs = start.elapsedNow().inWholeMilliseconds
@@ -135,6 +113,11 @@ class PiSpigotBenchmarkTest {
             ?: (stmt as? BytecodeBodyProvider)?.bytecodeBody()?.bytecodeFunction()
     }
 
+    private fun loadPiSpigotSource(): String {
+        val source = Files.readString(resolveExample("pi-bench.lyng"))
+        return source.substringBefore("\nval t0 = Instant()")
+    }
+
     private fun resolveExample(name: String): Path {
         val direct = Path.of("examples", name)
         if (Files.exists(direct)) return direct