* lib.c (acons): New function.

(set_diff): Optimize common case: list1 and list2
are the same, or list2 is substructure of list1.
Situations in which this won't be the case for variable bindings are
rare.

* lib.h (acons): Declared.

* match.c (match_line): Use acons rather than acons_new, when binding
variables that we know are new (the symbol is unbound).
When computing the set difference over bindings, use cons cell
equality, rather than symbol equality. Symbol equality is wrong
because a binding can be removed, and then a new binding can be
introduced using the same symbol. This must be treated as
a different binding.

1 files changed, 1 insertions, 0 deletions

diff --git a/lib.h b/lib.h
index 6dd743f9..d1323f23 100644
--- a/lib.h
+++ b/lib.h
@@ -376,6 +376,7 @@ val cobj(mem_t *handle, val cls_sym, struct cobj_ops *ops);
 val cobjp(val obj);
 mem_t *cobj_handle(val cobj, val cls_sym);
 val assoc(val list, val key);
+val acons(val list, val car, val cdr);
 val acons_new(val list, val key, val value);
 val *acons_new_l(val *list, val key, val *new_p);
 val alist_remove(val list, val keys);