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

[Michele La Monaca]

On Tue, Mar 4, 2014 at 1:05 AM, Michele La Monaca
<address@hidden> wrote:
>>> (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))))))
>
> After some pondering I realized that it would be valuable to provide
> this primitive in the library:
>
> (define (irregex-replace-match m str o)
>   (string-append
>     (substring str 0 (irregex-match-start-index m 0))
>     (apply string-append (reverse (irregex-apply-match m o)))
>     (substring str (irregex-match-end-index m 0) (string-length str))))

After some more mulling, I concluded that it would be even more
convenient to have a generalised version of irregex-replace-match
which also accepts lists of matches:

(irregex-replace-match match-or-list-of-matches str o)

On top of that, it would be easy to build irregex-replace/all semantics, too:

(define (irregex-replace/all irx str . o)
  (let ((ms (irregex-search/all irx str)))
    (if (pair? ms) (irregex-replace-match ms str o) str)))

(define (my-irregex-replace irx str . o)
  (let ((ms (irregex-search/all irx str)))
    (and (pair? ms) (irregex-replace-match ms str o))))

It would also be possible to easily implement less common actions like that:

(define (irregex-replace/2nd-and-4th irx str . o)
  (let ((ms (irregex-search/all irx str 4)))
    (if (pair? ms)
      (irregex-replace-match (list (list-ref ms 1) (list-ref ms 3)) str o)
      str)))

Michele