operator-length.go: the prefix operator '#' now accept iterator oeprand; it returns the index of the current item

operator-length.go

@@ -29,9 +29,8 @@ func evalLength(ctx ExprContext, self *term) (v any, err error) {
 	} else if isString(rightValue) {
 		s, _ := rightValue.(string)
 		v = len(s)
-		// } else {
-		// 	v = 1
-		// }
+	} else if it, ok := rightValue.(Iterator); ok {
+		v = it.Index()
 	} else {
 		err = self.errIncompatibleType(rightValue)
 	}