(define (read-on-row *params*)
;; Returns the last line in "myfile" which contains
;; substring "ON", otherwise #f
(call-with-input-file (hash-ref *params* "myfile")
(lambda (inp)
(for/first ([row (in-lines inp 'return-linefeed)]
#:when (string-contains? row "ON"))
row))))
(define (on-row-exists *params*)
;; Returns #t if there is line in "myfile" which contains
;; substring "ON", otherwise #f
(call-with-input-file (hash-ref *params* "myfile")
(lambda (inp)
(for/or ([row (in-lines inp 'return-linefeed)])
(string-contains? row "ON")))))
On Fri, Aug 19, 2016 at 9:18 PM, Pekka Niiranen <pekka.niira...@pp5.inet.fi>
wrote:
> Hello users,
>
> I would like to read lines from a file, process each line
> and return either the success of the operation or the processed line to
> another function located in another module.
>
> Below are two functions that work OK, but are in my opinion "ugly" because
> they use "set!".
>
> It there a way to make both functions work without "set!"?
>
>
> ;;------------------------------------------------------------
> (define (read-on-row *params*)
> ;; Returns the last line in "myfile" which contains
> ;; substring "ON", otherwise #f
>
> (define pdata #f) ;; I do not like this extra variable!
>
> (call-with-input-file (hash-ref *params* "myfile")
> (lambda (inp)
> (for/last ([row (in-lines inp 'return-linefeed)]
> #:when (string-contains? "ON" row))
> (set! pdata row))))
>
> pdata)
>
> ;;------------------------------------------------------------
>
> (define (on-row-exists *params*)
> ;; Returns #t if there is line in "myfile" which contains
> ;; substring "ON", otherwise #f
>
> (define found-on #f) ;; I do not like this extra variable!
>
> (call-with-input-file (hash-ref *params* "myfile")
> (lambda (inp)
> (for/last ([row (in-lines inp 'return-linefeed)]
> #:when (string-contains? "ON" row))
> (set! found-on #t))))
>
> found-on)
>
> -pekka-
>
>
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