Re: [Chicken-users] irregex-replace return value

[Alex Shinn]

On Sun, Mar 2, 2014 at 8:51 PM, Michele La Monaca <address@hidden> wrote:

While writing my own version of irregex-replace can be (hopefully) an enjoyable
6-line coding experience (btw, irregex-apply-match is not documented):

Oops, thanks, I'll document it.

(define (my-own-irregex-replace irx s . o)
  (let ((m (irregex-search irx s)))
    (and m (string-append
             (substring s 0 (irregex-match-start-index m 0))
             (apply string-append (reverse (irregex-apply-match m o)))
             (substring s (irregex-match-end-index m 0) (string-length s))))))

writing a customized version of irregex-replace/all means writing a real
non-elementary program.

It's probably not as complicated as you're imagining.

irregex-fold does most of the work:

#;2> (define (my-irregex-replace-all irx str . o)

  (irregex-fold

   irx

   (lambda (i m acc)

     (let ((m-start (irregex-match-start-index m 0)))

       (cons

        (+ 1 (car acc))

        (append (irregex-apply-match m o)

                (if (>= i m-start)

                    (cdr acc)

                    (cons (substring str i m-start) (cdr acc)))))))

   '(0)

   str

   (lambda (i acc)

     (let ((end (string-length str)))

       (values

        (apply

         string-append

         (reverse (if (>= i end)

                      (cdr acc)

                      (cons (substring str i end) (cdr acc)))))

        (car acc))))))

#;3> (my-irregex-replace-all '(+ digit) "one 1 two 22 three 333" "?")

"one ? two ? three ?"

3

; 2 values

I'll consider adding this utility, though.

-- 

Alex