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Oct-escape

Oct-escapep

Recognizer for oct-escape structures.

Signature
(oct-escapep x) → *

Definitions and Theorems

Function: oct-escapep

(defun oct-escapep (x)
  (declare (xargs :guard t))
  (let ((__function__ 'oct-escapep))
    (declare (ignorable __function__))
    (and (consp x)
         (cond ((or (atom x) (eq (car x) :one))
                (and (true-listp (cdr x))
                     (eql (len (cdr x)) 1)
                     (b* ((digit (std::da-nth 0 (cdr x))))
                       (oct-digit-char-p digit))))
               ((eq (car x) :two)
                (and (true-listp (cdr x))
                     (eql (len (cdr x)) 2)
                     (b* ((digit1 (std::da-nth 0 (cdr x)))
                          (digit2 (std::da-nth 1 (cdr x))))
                       (and (oct-digit-char-p digit1)
                            (oct-digit-char-p digit2)))))
               (t (and (eq (car x) :three)
                       (and (true-listp (cdr x))
                            (eql (len (cdr x)) 3))
                       (b* ((digit1 (std::da-nth 0 (cdr x)))
                            (digit2 (std::da-nth 1 (cdr x)))
                            (digit3 (std::da-nth 2 (cdr x))))
                         (and (oct-digit-char-p digit1)
                              (oct-digit-char-p digit2)
                              (oct-digit-char-p digit3)))))))))

Theorem: consp-when-oct-escapep

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