codegen: fix interpreter re-entrance

So multiple successive incremental Evals function correctly.

Also improve the following:
- Apply the same Eval API to vm0 and vm1
- parser: dot diagram display is now synchronous
- codegen: outsource complex code generation for readability
- vm1: Pop take the number of values to pop as operand

1 files changed, 41 insertions, 0 deletions

diff --git a/codegen/expression.go b/codegen/expression.go
new file mode 100644
index 0000000..b73f4da
--- /dev/null
+++ b/codegen/expression.go
@@ -0,0 +1,41 @@
+package codegen
+
+import (
+	"fmt"
+	"reflect"
+
+	"github.com/gnolang/parscan/parser"
+	"github.com/gnolang/parscan/vm1"
+)
+
+func postCallExpr(x extNode) error {
+	switch x.Child[0].Kind {
+	case parser.Ident:
+		var numOut int
+		s, _, ok := x.getSym(x.Child[0].Content(), "")
+		if !ok {
+			return fmt.Errorf("invalid symbol %s", x.Child[0].Content())
+		}
+		if i, ok := x.codeIndex(s); ok {
+			// Internal call is always relative to instruction pointer.
+			x.Emit(x.Node, vm1.Call, int64(i-len(x.Code)))
+		} else {
+			// External call, using absolute addr in symtable.
+			x.Emit(x.Node, vm1.CallX, int64(len(x.Child[1].Child)))
+			numOut = reflect.TypeOf(x.Data[s.index]).NumOut()
+		}
+		if !usedRet(x.anc) {
+			x.Emit(x.Node, vm1.Pop, int64(numOut))
+		}
+	}
+	return nil
+}
+
+func usedRet(n *parser.Node) bool {
+	switch n.Kind {
+	case parser.Undefined, parser.StmtBloc:
+		return false
+	default:
+		return true
+	}
+}