Recognizer for dec-expo-prefix structures.
(dec-expo-prefixp x) → *
Function:
(defun dec-expo-prefixp (x) (declare (xargs :guard t)) (let ((__function__ 'dec-expo-prefixp)) (declare (ignorable __function__)) (and (consp x) (cond ((or (atom x) (eq (car x) :locase-e)) (and (true-listp (cdr x)) (eql (len (cdr x)) 0) (b* nil t))) (t (and (eq (car x) :upcase-e) (and (true-listp (cdr x)) (eql (len (cdr x)) 0)) (b* nil t)))))))
Theorem:
(defthm consp-when-dec-expo-prefixp (implies (dec-expo-prefixp x) (consp x)) :rule-classes :compound-recognizer)