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• Binary

Bin-digit-string-p

Recognizer for strings whose characters are all 0 or 1.

Signature

(bin-digit-string-p x) → bool

Corner case: this accepts the empty string since all of its characters are bit digits.

Logically this is defined in terms of bin-digit-char-list*p. But in the execution, we use a char-based function that avoids exploding the string. This provides much better performance, e.g., on an AMD FX-8350 with CCL:

;; 0.53 seconds, no garbage
(let ((x "01001"))
  (time$ (loop for i fixnum from 1 to 10000000 do
               (str::bin-digit-string-p x))))

;; 0.99 seconds, 800 MB allocated
(let ((x "01001"))
  (time$ (loop for i fixnum from 1 to 10000000 do
               (str::bin-digit-char-list*p (explode x)))))

Definitions and Theorems

Function: bin-digit-string-p$inline

(defun bin-digit-string-p$inline (x)
  (declare (type string x))
  (let ((acl2::__function__ 'bin-digit-string-p))
    (declare (ignorable acl2::__function__))
    (mbe :logic (bin-digit-char-list*p (explode x))
         :exec (bin-digit-string-p-aux x 0 (length x)))))

Theorem: istreqv-implies-equal-bin-digit-string-p-1

(defthm istreqv-implies-equal-bin-digit-string-p-1
  (implies (istreqv x x-equiv)
           (equal (bin-digit-string-p x)
                  (bin-digit-string-p x-equiv)))
  :rule-classes (:congruence))

Subtopics

Bin-digit-string-p-aux