Fix #160: WriteString["stdout", ...] support

.gitignore

@@ -4,6 +4,8 @@ y.output
 test_rubi
 *.expred
 .DS_Store
+__debug_bin
+.vscode
 
 .idea/expreduce.iml
 

expreduce/builtin_system.go

@@ -234,14 +234,21 @@ func applyModuleFn(this expreduceapi.ExpressionInterface, es expreduceapi.EvalSt
 }
 
 func parseOutputStream(outputStreamDef expreduceapi.Ex) (string, int64, bool) {
+	// Handle string-only stream names like "stdout".
+	streamName, ok := outputStreamDef.(*atoms.String)
+	if ok {
+		// Use -1 as a placeholder for a missing index.
+		return streamName.GetValue(), -1, true
+	}
+
 	outputStream, isOutputStream := atoms.HeadAssertion(outputStreamDef, "System`OutputStream")
 	if !isOutputStream {
 		return "", -1, false
 	}
 	if outputStream.Len() != 2 {
 		return "", -1, false
 	}
-	streamName, ok := outputStream.GetPart(1).(*atoms.String)
+	streamName, ok = outputStream.GetPart(1).(*atoms.String)
 	if !ok {
 		return "", -1, false
 	}

expreduce/streammanager/streammanager.go

@@ -29,9 +29,20 @@ func NewStreamManager() expreduceapi.StreamManager {
 	return &sm
 }
 
+func (sm streamManagerImpl) fillMissingIndex(key *streamKey) {
+	if key.id == -1 {
+		if key.name == "stdout" {
+			key.id = 1
+		} else if key.name == "stdin" {
+			key.id = 2
+		}
+	}
+}
+
 // WriteString writes the toWrite string into the stream defined by streamName and streamIndex.
 func (sm streamManagerImpl) WriteString(streamName string, streamIndex int64, toWrite string) bool {
 	key := streamKey{id: streamIndex, name: streamName}
+	sm.fillMissingIndex(&key)
 	writer, hasWriter := sm.openStreams[key]
 	if !hasWriter {
 		return false