diff options
| -rw-r--r-- | lists/perm.lisp | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/lists/perm.lisp b/lists/perm.lisp index e1d8c77..4668a2b 100644 --- a/lists/perm.lisp +++ b/lists/perm.lisp @@ -1,6 +1,8 @@ (in-package "ACL2") (defun perm (x y) + (declare (xargs :guard (and (true-listp x) + (true-listp y)))) (cond ((atom x) (atom y)) ((member-equal (car x) y) |