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

[Michele La Monaca]

>> (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))))

On top of which is easier to build irregex-replace semantics:

(define (irregex-replace irx str . o)
  (let ((m (irregex-search irx str)))
    (if m (irregex-replace-match m str o) str)))

(define (my-irregex-replace irx str . o)
  (let ((m (irregex-search irx str)))
    (and m (irregex-replace-match m str o))))

I would also add this procedure:

(irregex-search/all <irx> <str> [max])

to provide a list of all (or max) matches.

By combining irregex-search/all and irregex-replace-match it's a
breeze to build an "irregex-replace/nth" semantic:

(define (irregex-replace/nth n irx str . o)
  (irregex-replace-match (car (reverse (irregex-search/all irx str n))) str o))

(irregex-replace/nth 4 'digit "1-2-3-4-5" "notprime")

=> 1-2-3-notprime-5


Michele