add IsEmpty

vector/vector.go

@@ -30,8 +30,8 @@ func (this *Vector) Conj(data any) *Vector {
 	return newVec
 }
 
-func String(this *Vector) string {
-	if this == nil {
+func (this *Vector) String() string {
+	if this.IsEmpty() {
 		return "[]"
 	}
 	var sb strings.Builder
@@ -41,10 +41,11 @@ func String(this *Vector) string {
 		sb.WriteRune(' ')
 	}
 	return sb.String()[:sb.Len()-1] + "]"
+
 }
 
-func (this *Vector) String() string {
-	return String(this)
+func (this *Vector) IsEmpty() bool {
+	return len(this._slice) == 0
 }
 
 func ToList(this *Vector) list.IList {