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• Charset-p

Str-count-leading-charset-fast

Fixnum optimized version of str-count-leading-charset.

Signature

(str-count-leading-charset-fast n x xl set) → n

Arguments

n — Current position in the string.
    Guard (natp n).

x — String we're iterating through.
    Guard (stringp x).

xl — Precomputed length of x.
    Guard (eql xl (length x)).

set — Set of characters we're counting.
    Guard (charset-p set).

Returns

n — Type (natp n).

Definitions and Theorems

Function: str-count-leading-charset-fast

(defun str-count-leading-charset-fast (n x xl set)
 (declare (xargs :guard (and (natp n)
                             (stringp x)
                             (charset-p set)
                             (eql xl (length x)))))
 (declare (type (unsigned-byte 60) n xl)
          (type string x))
 (declare (xargs :guard (<= n xl)))
 (let ((acl2::__function__ 'str-count-leading-charset-fast))
  (declare (ignorable acl2::__function__))
  (mbe :logic
       (let ((chars (nthcdr n (coerce x 'list))))
         (count-leading-charset chars set))
       :exec
       (b* (((when (eql n xl)) 0)
            ((the character char1) (char x n))
            ((the (unsigned-byte 60) n) (+ 1 n))
            ((when (char-in-charset-p char1 set))
             (the (integer 0 *)
                  (+ 1
                     (str-count-leading-charset-fast n x xl set)))))
         0))))

Theorem: natp-of-str-count-leading-charset-fast

(defthm natp-of-str-count-leading-charset-fast
  (b* ((n (str-count-leading-charset-fast n x xl set)))
    (natp n))
  :rule-classes :type-prescription)