This is a universal equivalence, introduced using ACL2::def-universal-equiv.
Function:
(defun fgl-ev-equiv (x y) (declare (xargs :non-executable t)) (declare (xargs :guard t)) (prog2$ (acl2::throw-nonexec-error 'fgl-ev-equiv (list x y)) (let ((env (fgl-ev-equiv-witness x y))) (and (equal (fgl-ev x env) (fgl-ev y env))))))
Theorem:
(defthm fgl-ev-equiv-necc (implies (not (and (equal (fgl-ev x env) (fgl-ev y env)))) (not (fgl-ev-equiv x y))))
Theorem:
(defthm fgl-ev-equiv-is-an-equivalence (and (booleanp (fgl-ev-equiv x y)) (fgl-ev-equiv x x) (implies (fgl-ev-equiv x y) (fgl-ev-equiv y x)) (implies (and (fgl-ev-equiv x y) (fgl-ev-equiv y z)) (fgl-ev-equiv x z))) :rule-classes (:equivalence))