1 files changed, 73 insertions, 0 deletions
diff --git a/vm0/func.go b/vm0/func.go
new file mode 100644
index 0000000..6c95383
--- /dev/null
+++ b/vm0/func.go
@@ -0,0 +1,73 @@
+package vm0
+
+import (
+	"reflect"
+	"strings"
+
+	"github.com/gnolang/parscan/parser"
+)
+
+var types = map[string]reflect.Type{
+	"int":    reflect.TypeOf(0),
+	"string": reflect.TypeOf(""),
+}
+
+func (i *Interp) callFunc(n *parser.Node) {
+	fp := i.fp
+	l := len(i.stack)
+	nargs := i.stack[l-1].(int)
+	args := make([]reflect.Value, nargs)
+	for j := range args {
+		args[nargs-j-1] = reflect.ValueOf(i.stack[l-2-j])
+	}
+	f := reflect.ValueOf(i.stack[l-2-nargs])
+	out := f.Call(args)
+	i.fp = fp
+	i.stack = i.stack[:l-2-nargs]
+	for _, v := range out {
+		i.push(v.Interface())
+	}
+}
+
+func (i *Interp) declareFunc(r *parser.Node, scope string) {
+	fname := r.Child[0].Content()
+
+	// Add symbols for input and output function arguments.
+	inArgs := r.Child[1].Child
+	fscope := strings.TrimPrefix(scope+"/"+fname+"/", "/")
+	in := make([]reflect.Type, len(inArgs))
+	for j, c := range inArgs {
+		i.sym[fscope+c.Content()] = j
+		in[j] = types[c.Child[0].Content()]
+	}
+	var out []reflect.Type
+	if len(r.Child) > 3 { // function has return values
+		if i.IsBlock(r.Child[2]) {
+			outArgs := r.Child[2].Child
+			out = make([]reflect.Type, len(outArgs))
+			for j, c := range outArgs {
+				out[j] = types[c.Content()]
+			}
+		} else {
+			out = []reflect.Type{types[r.Child[2].Content()]}
+		}
+	}
+	funT := reflect.FuncOf(in, out, false)
+
+	// Generate a wrapper function which will run function body AST.
+	f := reflect.MakeFunc(funT, func(args []reflect.Value) (res []reflect.Value) {
+		i.fp = len(i.stack) // fp will be restored by caller (callFunc).
+		for _, arg := range args {
+			i.push(arg.Interface())
+		}
+		i.Run(r.Child[len(r.Child)-1], fscope)
+		b := len(i.stack) - len(out)
+		for j := range out {
+			res = append(res, reflect.ValueOf(i.stack[b+j]))
+		}
+		return res
+	})
+
+	// Add a symbol for newly created func.
+	i.sym[scope+fname] = i.push(f.Interface()) - i.fp
+}