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Strsubst

Strsubst-aux

Fast implementation of strsubst.

Definitions and Theorems

Function: strsubst-aux

(defun strsubst-aux (old new x n xl oldl acc)
 (declare (type string old new x)
          (type (integer 0 *) n xl oldl)
          (xargs :guard (and (stringp old)
                             (stringp new)
                             (stringp x)
                             (natp n)
                             (natp xl)
                             (posp oldl)
                             (= oldl (length old))
                             (= xl (length x)))))
 (cond ((mbe :logic (zp oldl) :exec nil) acc)
       ((mbe :logic (zp (- (nfix xl) (nfix n)))
             :exec (>= n xl))
        acc)
       ((strprefixp-impl old x 0 n oldl xl)
        (let ((acc (revappend-chars new acc)))
          (strsubst-aux old new x
                        (the (integer 0 *)
                             (+ oldl (the (integer 0 *) (lnfix n))))
                        xl oldl acc)))
       (t (let ((acc (cons (char x n) acc)))
            (strsubst-aux old new x
                          (the (integer 0 *)
                               (+ 1 (the (integer 0 *) (lnfix n))))
                          xl oldl acc)))))

Theorem: character-listp-of-strsubst-aux

(defthm character-listp-of-strsubst-aux
 (implies (and (stringp old)
               (stringp new)
               (stringp x)
               (natp n)
               (posp oldl)
               (= oldl (length old))
               (= xl (length x))
               (character-listp acc))
          (character-listp (strsubst-aux old new x n xl oldl acc))))