bugfix: tail handles improper list.

* lib.c (tail): This low-level function is used by the
list accumulation routines. Because it doesn't handle
improper lists, looking for a null terminator, certain
things don't work, like the associativity of append.
For instance (append '(1 2) #(3) 4) works but not
(append (append '(1 2) #(3)) 4). Fixing tail so that it
terminates on any atom, rather than failing trying to
cdr through it.

1 files changed, 1 insertions, 1 deletions

diff --git a/lib.c b/lib.c
index 97d0eece..08deb233 100644
--- a/lib.c
+++ b/lib.c
@@ -615,7 +615,7 @@ loc listref_l(val list, val ind)
 
 loc tail(val cons)
 {
-  while (cdr(cons))
+  while (consp(cdr(cons)))
     cons = cdr(cons);
   return cdr_l(cons);
 }