From: Ricardo Wurmus <ricardo.wurmus@mdc-berlin.de>
To: Efraim Flashner <efraim@flashner.co.il>
Cc: guix-devel@gnu.org
Subject: Re: Adding wc to Bournish
Date: Tue, 14 Jun 2016 13:08:54 +0200 [thread overview]
Message-ID: <idja8ioxc1l.fsf@bimsb-sys02.mdc-berlin.net> (raw)
In-Reply-To: <20160614105037.GC10636@debian-netbook>
Efraim Flashner <efraim@flashner.co.il> writes:
>> It's already calling `((@@ (guix build bournish)
>> wc-l-command-implementation) ,@(delete "-l" args)), I could try changing
>> the ,@(delete part to ,@((@@ (guix build bournish) only-files) ,@(delete
>> "-l" args)) and then the various implementation functions will be just
>> printing the results
>>
>
> It turns out I forgot that calling only-files from wc-commands would
> make it evaluate too soon, so I stuck it inside the different
> implementations. Factoring out the check if a file exists or not could
> also apply to the ls-command-implementation too later.
I don’t understand this (but don’t let this delay you). I don’t see any
“only-files” in your patch. To delay evaluation you can always wrap
expressions in “(lambda _ ...)”.
I was thinking of a first simplification like this:
(define (existing-files file)
(catch 'system-error
(lambda ()
(stat file))
(lambda args
(let ((errno (system-error-errno args)))
(format (current-error-port) "~a: ~a~%"
file (strerror errno))
#f))))
(define (wc-print file)
(let-values (((lines chars)
(call-with-input-file file lines+chars)))
(format #t "~a ~a ~a~%" lines chars file)))
(define (wc-l-print file)
(let-values (((lines chars)
(call-with-input-file file lines+chars)))
(format #t "~a ~a~%" lines file)))
(define (wc-c-print file)
(let-values (((lines chars)
(call-with-input-file file lines+chars)))
(format #t "~a ~a~%" chars file)))
(define (wc-command-implementation files)
(for-each wc-print (filter existing-files files)))
(define (wc-l-command-implementation files)
(for-each wc-l-print (filter existing-files files)))
(define (wc-c-command-implementation files)
(for-each wc-c-print (filter existing-files files)))
Even at this point there’s a lot of repetition that we could get rid of,
but maybe that’s too zealous. Note that I didn’t follow this whole
discussion, so I could be completely off target.
~~ Ricardo
next prev parent reply other threads:[~2016-06-14 11:09 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-24 18:47 Adding wc to Bournish Efraim Flashner
2016-05-25 9:03 ` Ricardo Wurmus
2016-05-25 9:43 ` Efraim Flashner
2016-05-25 9:26 ` Ricardo Wurmus
2016-05-25 10:05 ` Efraim Flashner
2016-05-26 8:46 ` Ludovic Courtès
2016-05-26 17:50 ` Efraim Flashner
2016-05-26 19:27 ` Efraim Flashner
2016-05-27 13:37 ` Eric Bavier
2016-05-27 15:28 ` Taylan Ulrich Bayırlı/Kammer
2016-05-27 15:32 ` Thompson, David
2016-06-05 12:40 ` Efraim Flashner
2016-06-05 20:37 ` Ludovic Courtès
2016-06-07 7:41 ` Efraim Flashner
2016-06-08 15:43 ` Ludovic Courtès
2016-06-14 9:27 ` Efraim Flashner
2016-06-14 9:57 ` Ricardo Wurmus
2016-06-14 10:20 ` Efraim Flashner
2016-06-14 10:50 ` Efraim Flashner
2016-06-14 11:08 ` Ricardo Wurmus [this message]
2016-06-15 13:56 ` Ludovic Courtès
2016-06-15 20:28 ` Efraim Flashner
2016-06-23 8:34 ` Ludovic Courtès
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