list iterators now support start, stop e step

operand-iterator.go

@@ -133,29 +133,52 @@ func evalIterator(ctx ExprContext, self *term) (v any, err error) {
 
 		v = dc
 	} else if list, ok := firstChildValue.(*ListType); ok {
-		v = NewListIterator(list)
+		var args []any
+		if args, err = evalSibling(ctx, self.children, nil); err == nil {
+			v = NewListIterator(list, args)
+		}
 	} else {
-		var list *ListType
-		if list, err = evalChildren(ctx, self.children, firstChildValue); err == nil {
-			v = NewListIterator(list)
+		var list []any
+		if list, err = evalSibling(ctx, self.children, firstChildValue); err == nil {
+			v = NewArrayIterator(list)
 		}
 	}
 	return
 }
 
-func evalChildren(ctx ExprContext, terms []*term, firstChildValue any) (list *ListType, err error) {
-	items := make(ListType, len(terms))
+// func evalChildren(ctx ExprContext, terms []*term, firstChildValue any) (list *ListType, err error) {
+// 	items := make(ListType, len(terms))
+// 	for i, tree := range terms {
+// 		var param any
+// 		if i == 0 && firstChildValue != nil {
+// 			param = firstChildValue
+// 		} else if param, err = tree.compute(ctx); err != nil {
+// 			break
+// 		}
+// 		items[i] = param
+// 	}
+// 	if err == nil {
+// 		list = &items
+// 	}
+// 	return
+// }
+
+func evalSibling(ctx ExprContext, terms []*term, firstChildValue any) (list []any, err error) {
+	items := make([]any, 0, len(terms))
 	for i, tree := range terms {
 		var param any
-		if i == 0 && firstChildValue != nil {
+		if i == 0 {
+			if firstChildValue == nil {
+				continue
+			}
 			param = firstChildValue
 		} else if param, err = tree.compute(ctx); err != nil {
 			break
 		}
-		items[i] = param
+		items = append(items, param)
 	}
 	if err == nil {
-		list = &items
+		list = items
 	}
 	return
 }