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authorMasaya Tojo <masaya@tojo.tokyo>2022-07-16 15:35:48 +0900
committerMasaya Tojo <masaya@tojo.tokyo>2022-07-16 15:35:48 +0900
commitf23d7365a67c9b73a767162b728ed3fbdb3b79ac (patch)
treea0d3544accf0357e242cb33bfdb1f1905042390e
parent8ada9230a681e8c1ee23686815c866d6eebde7e8 (diff)
lists: perm: Add guards.
-rw-r--r--lists/perm.lisp2
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)