Get the extension field from a fundef.
This is an ordinary field accessor created by fty::defprod.
Function:
(defun fundef->extension$inline (x) (declare (xargs :guard (fundefp x))) (declare (xargs :guard t)) (let ((__function__ 'fundef->extension)) (declare (ignorable __function__)) (mbe :logic (b* ((x (and t x))) (bool-fix (cdr (std::da-nth 0 x)))) :exec (cdr (std::da-nth 0 x)))))
Theorem:
(defthm booleanp-of-fundef->extension (b* ((extension (fundef->extension$inline x))) (booleanp extension)) :rule-classes :rewrite)
Theorem:
(defthm fundef->extension$inline-of-fundef-fix-x (equal (fundef->extension$inline (fundef-fix x)) (fundef->extension$inline x)))
Theorem:
(defthm fundef->extension$inline-fundef-equiv-congruence-on-x (implies (fundef-equiv x x-equiv) (equal (fundef->extension$inline x) (fundef->extension$inline x-equiv))) :rule-classes :congruence)