Basic equivalence relation for modalist structures.
Function:
(defun modalist-equiv$inline (x y) (declare (xargs :guard (and (modalist-p x) (modalist-p y)))) (equal (modalist-fix x) (modalist-fix y)))
Theorem:
(defthm modalist-equiv-is-an-equivalence (and (booleanp (modalist-equiv x y)) (modalist-equiv x x) (implies (modalist-equiv x y) (modalist-equiv y x)) (implies (and (modalist-equiv x y) (modalist-equiv y z)) (modalist-equiv x z))) :rule-classes (:equivalence))
Theorem:
(defthm modalist-equiv-implies-equal-modalist-fix-1 (implies (modalist-equiv x x-equiv) (equal (modalist-fix x) (modalist-fix x-equiv))) :rule-classes (:congruence))
Theorem:
(defthm modalist-fix-under-modalist-equiv (modalist-equiv (modalist-fix x) x) :rule-classes (:rewrite :rewrite-quoted-constant))
Theorem:
(defthm equal-of-modalist-fix-1-forward-to-modalist-equiv (implies (equal (modalist-fix x) y) (modalist-equiv x y)) :rule-classes :forward-chaining)
Theorem:
(defthm equal-of-modalist-fix-2-forward-to-modalist-equiv (implies (equal x (modalist-fix y)) (modalist-equiv x y)) :rule-classes :forward-chaining)
Theorem:
(defthm modalist-equiv-of-modalist-fix-1-forward (implies (modalist-equiv (modalist-fix x) y) (modalist-equiv x y)) :rule-classes :forward-chaining)
Theorem:
(defthm modalist-equiv-of-modalist-fix-2-forward (implies (modalist-equiv x (modalist-fix y)) (modalist-equiv x y)) :rule-classes :forward-chaining)