* lib.c (listref, listref_l): Negative indices must have semantics

consistent with vecref and ranges.

1 files changed, 4 insertions, 1 deletions

diff --git a/lib.c b/lib.c
index 29049969..3dd57738 100644
--- a/lib.c
+++ b/lib.c
@@ -310,7 +310,7 @@ val sixth(val cons)
 val listref(val list, val ind)
 {
   if (lt(ind, zero))
-    return nil;
+    ind = plus(ind, length_list(list));
   for (; gt(ind, zero); ind = minus(ind, one))
     list = cdr(list);
   return car(list);
@@ -321,6 +321,9 @@ val *listref_l(val list, val ind)
   val olist = list;
   val oind = ind;
 
+  if (lt(ind, zero))
+    ind = plus(ind, length_list(list));
+
   for (; gt(ind, zero) && list; ind = minus(ind, one))
     list = cdr(list);
   if (consp(list))