Thank you guys,
both functions work. Looks like single function (for/or) could be used
if the calling side handles #f, #t and a list.
Another issue:
I am planning to support both Unix and Windows, but have not found
a way to define 'return-linefeed as system-wide default (aside using
global variable):
Whenever one does file-I/O; 'return-linefeed is used as newline.
I do like not to be forced to give the 3rd parameter (return-linefeed)
like below
(in-lines inp 'return-linefeed)
-pekka-
On 20/08/16 02:47, Gustavo Massaccesi wrote:
> Minor fix: In the first function "read-on-row" you must replace
> for/first with for/last.
>
> Gustavo
>
> PS for Pekka: In this case it's better to use for/last and for/or, but
> in more complicated cases you can try with for/fold.
>
>
> On Fri, Aug 19, 2016 at 10:34 AM, WarGrey Gyoudmon Ju
> <juzhenli...@gmail.com> wrote:
>> (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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