		Search-engine friendly clone of the ACL2 documentation.

Equal-op

Equal-opp

Recognizer for equal-op structures.

Signature
(equal-opp x) → *

Definitions and Theorems

Function: equal-opp

(defun equal-opp (x)
  (declare (xargs :guard t))
  (let ((__function__ 'equal-opp))
    (declare (ignorable __function__))
    (and (consp x)
         (cond ((or (atom x) (eq (car x) :is.eq))
                (and (true-listp (cdr x))
                     (eql (len (cdr x)) 0)
                     (b* nil t)))
               (t (and (eq (car x) :is.neq)
                       (and (true-listp (cdr x))
                            (eql (len (cdr x)) 0))
                       (b* nil t)))))))

Theorem: consp-when-equal-opp

(defthm consp-when-equal-opp
  (implies (equal-opp x) (consp x))
  :rule-classes :compound-recognizer)