Re: Adding wc to Bournish

[Ludovic Courtès]

Efraim Flashner <address@hidden> skribis:

> On Sun, Jun 05, 2016 at 10:37:12PM +0200, Ludovic Courtès wrote:

[...]

>> 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 should be be ‘read-and-compile’, not ‘compile’.)

Done in f82c58539e1f7b9b864e68ea2ab0c6a17c15fbb5.  Take a look at
tests/bournish.scm for examples of what is expected.

> From ebce5076177314bfd17a53019b3f6b6888762b01 Mon Sep 17 00:00:00 2001
> From: Efraim Flashner <address@hidden>
> Date: Sun, 22 May 2016 14:56:06 +0300
> Subject: [PATCH] bournish: Add `wc' command.
>
> * guix/build/bournish.scm (file-size, wc-c-command, wc-l-command,
> lines+chars, wc-command, wc-command-implementation): New variables.
> (%commands): Add wc command.

[...]

> +(define* (wc-command-implementation filelist #:optional args)

‘files’, not ‘filelist’.

> +  (let ((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))))

‘stat’ rather than ‘fstat’.

> +    (for-each
> +      (lambda (file)
> +        (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)))))
> +      files)))

OK.

> +(define (wc-command args . rest)
> +  (let* ((flags (cond ((string=? args "-l") #\l)
> +                      ((string=? args "-c") #\c)
> +                      (else #\nul))))    ; no flags, "args" is a file

I’d rather make it:

  (define (wc-commands . args)
    (cond ((member "-l" args) …)
          ((member "-c" args) …)
          (else …)))

Instead of the #\nul thing, I think it’d be best to have separate
procedures for -l, -c, and the other case.

> +    ((@@ (guix build bournish) wc-command-implementation)
> +     (if (char=? flags #\nul) (cons args rest) rest) flags)))

This is still not emitting code.  :-)  IOW, there should be a quasiquote
here.

You can see that by running:

  (use-modules (system base compile) (guix build bournish))
  (read-and-compile (open-input-string "wc -l foo")
                    #:from %bournish-language #:to 'scheme)

This should return something like:

  `((@ (guix build bournish) wc-l-command-implementation) '("foo"))

Makes sense?  We’re almost done.

Please take a look at
<https://www.gnu.org/software/guix/manual/html_node/Coding-Style.html>
to make the last review super fast.  ;-)

Thank you!

Ludo’.