Re: [PATCH] Add 'guix hash'.

[ludo@gnu.org (Ludovic Courtès)]

Nikita Karetnikov <nikita@karetnikov.org> skribis:

>> I think it’d be nice to have a ‘warning’ procedure in (guix ui), so
>> things are uniform.  Furthermore, ‘guix-main’ could do:
>
>>   (parameterize ((current-script-name arg0))
>>     ...)
>
>> so that ‘warning’ and similar procedures could pick up the program
>> name from there.
>
> Not sure how to do it.  How can I get the result of 'guix-main' from a
> relevant script (e.g., 'guix/scripts/hash.scm')?
>
> I assume that 'parameterize' should be placed inside 'guix-main'.  But
> how can 'warning' access its internals?  Note that I'm new to
> 'parameterize' and I'm not really comfortable with it.  (Yep, I've read
> the manual.)

‘parameterize’ sets dynamically-scoped variables (or “parameters”, in
SRFI-39 terms).  So for instance:

  (let* ((p (make-parameter 'outside))
         (f (lambda () (format #f "i am ~a" (p)))))
    (parameterize ((p 'inside))
      (f)))

  ⇒ "i am inside"

It’s like ‘current-input-port’ & co.

>> Would you like to work on this, in a separate patch?
>
> Yes, I'd like to push it prior to 'guix hash'.  But it seems that you'll
> do all the work if you answer my questions.  So feel free to push if the
> patch is just a couple of lines.

OK, done.

>> I was thinking that it might be enough to list the supported formats
>> in the manual, and not in --help, which should remain concise.  WDYT?
>
> Of course, it should be concise but also helpful.  I was puzzled when I
> saw it for the first time.  So I still think that we should mention the
> formats in the output of '--help'.  I'll create a patch for
> 'guix download' if you agree.

OK.

>>>> Also, could you add an entry in the manual (with a couple of
>>>> sentences explaining when users should care about this tool, and
>>>> what it does), as well as a line in po/POTFILES.in?
>
>>> Done.  But what is a translatable string?  Is it a string that should
>>> be i18n'd?
>
>> Yes, introduced by a call to the ‘gettext’ procedure, of which ‘_’ is
>> an alias.
>
> Why should we keep track of such files?

Because ‘xgettext’ extracts translatable strings from files listed
therein (info "(gettext) po/POTFILES.in").

> Also, what is the purpose of 'let' in 'guix-main'?  If I get it right,
> it's used to isolate some functions [1].  But 'option?' is not a
> top-level function.  So why bother?  (I expect it's not that easy.)

Yeah, I’d have written:

  (define (guix-main ...)
    (define (option? x) ...)
    (initialize-guix)
    (match args ...))

But it’s basically equivalent.

Ludo’.