Optimize int range loops and add benchmark gating

lynglib/src/commonTest/kotlin/NestedRangeBenchmarkTest.kt

@@ -0,0 +1,51 @@
+/*
+ * 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 kotlinx.coroutines.test.runTest
+import net.sergeych.lyng.Benchmarks
+import net.sergeych.lyng.eval
+import net.sergeych.lyng.obj.ObjInt
+import kotlin.time.TimeSource
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class NestedRangeBenchmarkTest {
+    @Test
+    fun benchmarkHappyNumbersNestedRanges() = runTest {
+        if (!Benchmarks.enabled) return@runTest
+        val script = """
+            fun naiveCountHappyNumbers() {
+                var count = 0
+                for( n1 in 0..9 )
+                    for( n2 in 0..9 )
+                        for( n3 in 0..9 )
+                            for( n4 in 0..9 )
+                                for( n5 in 0..9 )
+                                    for( n6 in 0..9 )
+                                        if( n1 + n2 + n3 == n4 + n5 + n6 ) count++
+                count
+            }
+            naiveCountHappyNumbers()
+        """.trimIndent()
+
+        val start = TimeSource.Monotonic.markNow()
+        val result = eval(script) as ObjInt
+        val elapsedMs = start.elapsedNow().inWholeMilliseconds
+        println("[DEBUG_LOG] [BENCH] nested-happy elapsed=${elapsedMs} ms")
+        assertEquals(55252L, result.value)
+    }
+}