Simplify toplevel read.

[mes.git] / lib.c

diff --git a/lib.c b/lib.c
index f1cb8e948d52a0e8ff7730cb17d973919e7887ff..b252ef1a014e8cce6b0ccdda49ad874492e93f11 100644 (file)
--- a/lib.c
+++ b/lib.c
@@ -56,6 +56,16 @@ list (scm *x) ///((args . n))
   return x;
 }
 
+scm *
+list_ref (scm *x, scm *k)
+{
+  assert (x->type == PAIR);
+  assert (k->type == NUMBER);
+  int n = k->value;
+  while (n-- && x->cdr != &scm_nil) x = x->cdr;
+  return x != &scm_nil ? x->car : &scm_undefined;
+}
+
 scm *
 vector_to_list (scm *v)
 {