Basic equivalence relation for feat structures.
Function:
(defun feat-equiv$inline (acl2::x acl2::y) (declare (xargs :guard (and (featp acl2::x) (featp acl2::y)))) (equal (feat-fix acl2::x) (feat-fix acl2::y)))
Theorem:
(defthm feat-equiv-is-an-equivalence (and (booleanp (feat-equiv x y)) (feat-equiv x x) (implies (feat-equiv x y) (feat-equiv y x)) (implies (and (feat-equiv x y) (feat-equiv y z)) (feat-equiv x z))) :rule-classes (:equivalence))
Theorem:
(defthm feat-equiv-implies-equal-feat-fix-1 (implies (feat-equiv acl2::x x-equiv) (equal (feat-fix acl2::x) (feat-fix x-equiv))) :rule-classes (:congruence))
Theorem:
(defthm feat-fix-under-feat-equiv (feat-equiv (feat-fix acl2::x) acl2::x) :rule-classes (:rewrite :rewrite-quoted-constant))
Theorem:
(defthm equal-of-feat-fix-1-forward-to-feat-equiv (implies (equal (feat-fix acl2::x) acl2::y) (feat-equiv acl2::x acl2::y)) :rule-classes :forward-chaining)
Theorem:
(defthm equal-of-feat-fix-2-forward-to-feat-equiv (implies (equal acl2::x (feat-fix acl2::y)) (feat-equiv acl2::x acl2::y)) :rule-classes :forward-chaining)
Theorem:
(defthm feat-equiv-of-feat-fix-1-forward (implies (feat-equiv (feat-fix acl2::x) acl2::y) (feat-equiv acl2::x acl2::y)) :rule-classes :forward-chaining)
Theorem:
(defthm feat-equiv-of-feat-fix-2-forward (implies (feat-equiv acl2::x (feat-fix acl2::y)) (feat-equiv acl2::x acl2::y)) :rule-classes :forward-chaining)