tasks a-s

Task/Queue-Definition/ACL2/queue-definition.acl2

@@ -0,0 +1,14 @@
+(defun enqueue (x xs)
+   (cons x xs))
+
+(defun dequeue (xs)
+   (declare (xargs :guard (and (consp xs)
+                               (true-listp xs))))
+   (if (or (endp xs) (endp (rest xs)))
+       (mv (first xs) nil)
+       (mv-let (x ys)
+               (dequeue (rest xs))
+          (mv x (cons (first xs) ys)))))
+
+(defun empty (xs)
+   (endp xs))