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Isuffix

Isuffixp

Recognizer for isuffix structures.

Signature
(isuffixp x) → *

Definitions and Theorems

Function: isuffixp

(defun isuffixp (x)
  (declare (xargs :guard t))
  (and (consp x)
       (cond ((or (atom x) (eq (car x) :u))
              (and (b* ((unsigned (cdr x)))
                     (usuffixp unsigned))))
             ((eq (car x) :l)
              (and (b* ((length (cdr x)))
                     (lsuffixp length))))
             ((eq (car x) :ul)
              (and (consp (cdr x))
                   (b* ((unsigned (car (cdr x)))
                        (length (cdr (cdr x))))
                     (and (usuffixp unsigned)
                          (lsuffixp length)))))
             (t (and (eq (car x) :lu)
                     (and (consp (cdr x)))
                     (b* ((length (car (cdr x)))
                          (unsigned (cdr (cdr x))))
                       (and (lsuffixp length)
                            (usuffixp unsigned))))))))

Theorem: consp-when-isuffixp

(defthm consp-when-isuffixp
  (implies (isuffixp x) (consp x))
  :rule-classes :compound-recognizer)