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• Octal

Octal-digit-to-char

Convert a number from 0-7 into a octal character.

Signature

(octal-digit-to-char n) → *

ACL2 has a built-in version of this function, digit-to-char, but octal-digit-to-char is faster:

(defconstant *codes*
  (loop for i from 0 to 7 collect i))

;; .114 seconds, no garbage
(time (loop for i fixnum from 1 to 10000000 do
            (loop for c in *codes* do (str::octal-digit-to-char c))))

;; .379 seconds, no garbage
(time (loop for i fixnum from 1 to 10000000 do
            (loop for c in *codes* do (digit-to-char c))))

Definitions and Theorems

Function: octal-digit-to-char$inline

(defun octal-digit-to-char$inline (n)
  (declare (type (unsigned-byte 3) n))
  (let ((acl2::__function__ 'octal-digit-to-char))
    (declare (ignorable acl2::__function__))
    (mbe :logic (digit-to-char n)
         :exec (code-char (the (unsigned-byte 8) (+ 48 n))))))