astvm eval of 'when'

compiler/src/prog8/CompilerMain.kt

@@ -63,7 +63,8 @@ private fun compileMain(args: Array<String>) {
 
     val filepath = Paths.get(moduleFile).normalize()
 
-    val (programAst, programName) = compileProgram(filepath, optimize, optimizeInlining, writeVmCode, writeAssembly)
+    val (programAst, programName) = compileProgram(filepath, optimize, optimizeInlining,
+            !launchAstVm, writeVmCode, writeAssembly)
 
     if(launchAstVm) {
         println("\nLaunching AST-based vm...")

compiler/src/prog8/compiler/Main.kt

@@ -24,7 +24,8 @@ import kotlin.system.measureTimeMillis
 
 fun compileProgram(filepath: Path,
                    optimize: Boolean, optimizeInlining: Boolean,
-                   writeVmCode: Boolean, writeAssembly: Boolean): Pair<Program, String?> {
+                   generateVmCode: Boolean, writeVmCode: Boolean,
+                   writeAssembly: Boolean): Pair<Program, String?> {
     lateinit var programAst: Program
     var programName: String? = null
 
@@ -89,6 +90,7 @@ fun compileProgram(filepath: Path,
             // printAst(programAst)
             // namespace.debugPrint()
 
+            if(generateVmCode) {
                 // compile the syntax tree into stackvmProg form, and optimize that
                 val compiler = Compiler(programAst)
                 val intermediate = compiler.compile(compilerOptions)
@@ -111,6 +113,7 @@ fun compileProgram(filepath: Path,
                     programName = assembly.name
                 }
             }
+        }
         println("\nTotal compilation+assemble time: ${totalTime / 1000.0} sec.")
 
     } catch (px: ParsingFailedError) {

compiler/src/prog8/vm/astvm/AstVm.kt

@@ -442,6 +442,23 @@ class AstVm(val program: Program) {
                     }
                 } while (!condition.asBoolean)
             }
+            is WhenStatement -> {
+                val condition=evaluate(stmt.condition, evalCtx)
+                for(choice in stmt.choices) {
+                    if(choice.value==null) {
+                        // the 'else' choice
+                        executeAnonymousScope(choice.statements)
+                        break
+                    } else {
+                        val value = choice.value.constValue(evalCtx.program) ?: throw VmExecutionException("can only use const values in when choices ${choice.position}")
+                        val rtval = RuntimeValue.from(value, evalCtx.program.heap)
+                        if(condition==rtval) {
+                            executeAnonymousScope(choice.statements)
+                            break
+                        }
+                    }
+                }
+            }
             else -> {
                 TODO("implement $stmt")
             }

examples/test.p8

@@ -16,8 +16,8 @@
             4 -> {
                 Y=7
             }
-            5 -> Y=5
             else -> A=99
+            5 -> Y=5        ; @todo error; else already seen
         }
     }