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• Cases

Downcase-char-str

Convert a character into a lower-case one-element string.

Signature

(downcase-char-str c) → str

Returns

str — Type (stringp str).

(downcase-char-str c) is logically equal to:

(implode (downcase-char c))

But we store these strings in a table so that they don't have to be recomputed. This is mainly useful to reduce the creation of temporary strings during downcase-first.

Definitions and Theorems

Function: make-downcase-first-strtbl

(defun make-downcase-first-strtbl (n)
  (declare (xargs :guard (and (natp n) (<= n 255))))
  (cons (cons n
              (implode (list (downcase-char (code-char n)))))
        (if (zp n)
            nil
          (make-downcase-first-strtbl (- n 1)))))

Function: downcase-char-str$inline

(defun downcase-char-str$inline (c)
  (declare (type character c))
  (let ((acl2::__function__ 'downcase-char-str))
    (declare (ignorable acl2::__function__))
    (mbe :logic (implode (list (downcase-char c)))
         :exec (aref1 '*downcase-first-strtbl*
                      *downcase-first-strtbl*
                      (char-code c)))))

Theorem: stringp-of-downcase-char-str

(defthm stringp-of-downcase-char-str
  (b* ((str (downcase-char-str$inline c)))
    (stringp str))
  :rule-classes :type-prescription)