Make nicer primitive functions for car/cdr

If it isn't a CONS, we return NIL instead of failing.  This way, we
can use it in our general iteration functions.  Eventually the actual
runtime would use this as well.  The macros are mostly for internal
use to do assignment etc.

1 files changed, 3 insertions, 0 deletions

diff --git a/alisp.h b/alisp.h
index c3d25c3..e9694d9 100644
--- a/alisp.h
+++ b/alisp.h
@@ -126,6 +126,9 @@ vec_t *as_vec(lisp_t *);
 #define CAR(L) (as_cons(L)->car)
 #define CDR(L) (as_cons(L)->cdr)
 
+lisp_t *car(lisp_t *);
+lisp_t *cdr(lisp_t *);
+
 /// Pointer tagging scheme for lisps
 
 typedef enum Tag