iter-list.go: implemntation of the ExtInterface and coperation reset

iter-list.go

@@ -4,7 +4,10 @@
 // iter-list.go
 package expr
 
-import "io"
+import (
+	"fmt"
+	"io"
+)
 
 type ListIterator struct {
 	a     *ListType
@@ -34,12 +37,26 @@ func NewAnyIterator(value any) (it *ListIterator) {
 	return
 }
 
-func (it *ListIterator) HasOperation(name string) bool {
+func (it *ListIterator) String() string {
-	return false
+	var l = 0
+	if it.a != nil {
+		l = len(*it.a)
+	}
+	return fmt.Sprintf("$(#%d)", l)
 }
 
-func (it *ListIterator) CallOperation(name string, args []any) (any, error) {
+func (it *ListIterator) HasOperation(name string) bool {
-	return nil, errNoOperation(name)
+	yes := name == resetName
+	return yes
+}
+
+func (it *ListIterator) CallOperation(name string, args []any) (v any, err error) {
+	if name == resetName {
+		v, err = it.Reset()
+	} else {
+		err = errNoOperation(name)
+	}
+	return
 }
 
 func (it *ListIterator) Current() (item any, err error) {
@@ -56,15 +73,14 @@ func (it *ListIterator) Next() (item any, err error) {
 	if item, err = it.Current(); err != io.EOF {
 		it.index++
 	}
-	// if it.index < len(it.a) {
-	// 	item = it.a[it.index]
-	// 	it.index++
-	// } else {
-	// 	err = io.EOF
-	// }
 	return
 }
 
 func (it *ListIterator) Index() int {
 	return it.index - 1
 }
+
+func (it *ListIterator) Reset() (bool, error) {
+	it.index = 0
+	return true, nil
+}