add pic_list_ref and pic_list_tail

2014-01-22 20:57:05 +09:00
parent 799e26cff0
commit a443d9e3f6
2 changed files with 18 additions and 0 deletions
@@ -29,6 +29,9 @@ pic_value pic_cadr(pic_state *, pic_value);
 pic_value pic_cdar(pic_state *, pic_value);
 pic_value pic_cddr(pic_state *, pic_value);

+pic_value pic_list_tail(pic_state *, pic_value ,int);
+pic_value pic_list_ref(pic_state *, pic_value, int);
+
 #if defined(__cplusplus)
 }
 #endif
@@ -180,6 +180,21 @@ pic_cddr(pic_state *pic, pic_value v)
  return pic_cdr(pic, pic_cdr(pic, v));
 }

+pic_value
+pic_list_tail(pic_state *pic, pic_value list, int i)
+{
+  while (i-- > 0) {
+    list = pic_cdr(pic, list);
+  }
+  return list;
+}
+
+pic_value
+pic_list_ref(pic_state *pic, pic_value list, int i)
+{
+  return pic_car(pic, pic_list_tail(pic, list, i));
+}
+
 static pic_value
 pic_pair_pair_p(pic_state *pic)
 {