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Re: Adding wc to Bournish
From: |
Efraim Flashner |
Subject: |
Re: Adding wc to Bournish |
Date: |
Tue, 7 Jun 2016 10:41:55 +0300 |
User-agent: |
Mutt/1.6.1 (2016-04-27) |
On Sun, Jun 05, 2016 at 10:37:12PM +0200, Ludovic Courtès wrote:
> Efraim Flashner <address@hidden> skribis:
> > +
> > +(define* (wc-command-implementation file #:optional args)
> > + (let-values (((lines chars)
> > + (call-with-input-file file lines+chars)))
> > + (match args
> > + (#\l
> > + (format #t "~a ~a~%" lines file))
> > + (#\c
> > + (format #t "~a ~a~%" chars file))
> > + (_
> > + (format #t "~a ~a ~a~%" lines chars file)))))
> > +
> > +(define (wc-command args . rest)
> > + (let* ((flags (cond ((string=? args "-l") #\l)
> > + ((string=? args "-c") #\c)
> > + (else #\nul))) ; no flags, "args" is a file
> > + (files (filter (lambda (file)
> > + (catch 'system-error
> > + (lambda ()
> > + (lstat file))
> > + (lambda args
> > + (let ((errno (system-error-errno args)))
> > + (format (current-error-port) "~a: ~a~%"
> > + file (strerror errno))
> > + #f))))
> > + (if (char=? flags #\nul) (cons args rest) rest))))
> > + (for-each
> > + (lambda (file)
> > + ((@@ (guix build bournish) wc-command-implementation) file flags))
> > + files)))
>
> As discussed at
> <https://lists.gnu.org/archive/html/guix-devel/2016-05/msg00782.html>,
> remember that ‘wc-command’ is called by the compiler to generate Scheme
> code from the input shell code. Thus, it must emit code that does the
> job. However, here, it does the job directly, at compilation time, and
> emits the result of ‘for-each’ as code.
copied from that email:
Thus, you must similarly distinguish those two stages by providing:
1. A ‘wc-command-implementation’ procedure that implements ‘wc’;
2. A ‘wc-command’ procedure that emits the code that calls
wc-command-implementation’; so something like:
(define (wc-command args)
`((@@ (guix build bournish) wc-command-implementation) ,@args))
Better yet, ‘wc-command’ could check for the presence of “-l” or “-c” at
compile time and emit a call to the right thing.
>
> I’ll commit a couple of fixes for bugs I just found and that prevent us
> from doing:
>
> (compile "ls" #:from %bournish-language #:to 'scheme).
>
> This is useful to clearly understand what code is generated from the
> input.
>
> Ludo’.
I've refactored the code so now in wc-command it checks if theres a flag
or not, and then passes the list of files to wc-command-implementation
to do the actual computation.
Does it make sense to switch it to something like the case-lambda setup
that `ls' uses or is for-each ok?
--
Efraim Flashner <address@hidden> אפרים פלשנר
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- Re: Adding wc to Bournish, Efraim Flashner, 2016/06/05
- Re: Adding wc to Bournish, Ludovic Courtès, 2016/06/05
- Re: Adding wc to Bournish,
Efraim Flashner <=
- Re: Adding wc to Bournish, Ludovic Courtès, 2016/06/08
- Re: Adding wc to Bournish, Efraim Flashner, 2016/06/14
- Re: Adding wc to Bournish, Ricardo Wurmus, 2016/06/14
- Re: Adding wc to Bournish, Efraim Flashner, 2016/06/14
- Re: Adding wc to Bournish, Efraim Flashner, 2016/06/14
- Re: Adding wc to Bournish, Ricardo Wurmus, 2016/06/14
- Re: Adding wc to Bournish, Ludovic Courtès, 2016/06/15
- Re: Adding wc to Bournish, Efraim Flashner, 2016/06/15
- Re: Adding wc to Bournish, Ludovic Courtès, 2016/06/23