diff --git a/operand-list.go b/operand-list.go
index b82a9bb..c7183d8 100644
--- a/operand-list.go
+++ b/operand-list.go
@@ -42,6 +42,10 @@ func (ls *ListType) ToString(opt FmtOpt) string {
 	return sb.String()
 }
 
+func (ls *ListType) String() string {
+	return ls.ToString(0)
+}
+
 // -------- list term
 func newListTermA(args ...*term) *term {
 	return newListTerm(args)