From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: Enhanced 'warning'
Date: Thu, 18 Apr 2013 13:55:13 +0200
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In-Reply-To: <871ua85t4w.fsf@karetnikov.org> (Nikita Karetnikov's message of
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To: Nikita Karetnikov <nikita@karetnikov.org>
Cc: bug-guix@gnu.org

Nikita Karetnikov <nikita@karetnikov.org> skribis:

>> I think it=E2=80=99d be nice to have a =E2=80=98warning=E2=80=99 procedu=
re in (guix ui), so
>> things are uniform.
>
> It think it might be better to have a single 'warning' macro which could
> handle several cases (errors, warnings and similar things).  (Actually,
> 'guix hash' should use errors, not warnings.)

Yes, you=E2=80=99re right.

> Here is a simplified version:
>
> (define-syntax define-output-macro

Rather: =E2=80=98define-diagnostic=E2=80=99.

>   (syntax-rules ()
>     ((_ name prefix)
>      (define-syntax name
>        (lambda (x)
>          (syntax-case x (_ N_)
>            ((name (_ str))
>             (with-syntax ((prefix (datum->syntax x prefix)))
>               #'(display (string-append prefix str "\n"))))
>            ((name (N_ str1 str2))
>             (with-syntax ((prefix (datum->syntax x prefix)))
>               #'(display (string-append prefix str1 str2 "\n"))))))))))

You should reuse the body of the current =E2=80=98warning=E2=80=99 macro, t=
hough.

> (define-output-macro warning "warning: ")
> (define-output-macro error* "error: ")

You could use =E2=80=98report-error=E2=80=99 to avoid name clashes.

But I think =E2=80=98leave=E2=80=99 should be enough, no?

> scheme@(guile-user)> (warning (_ "foo"))
> warning: foo
>
> scheme@(guile-user)> (error* (N_ "foo" "bar"))
> error: foobar

Note that =E2=80=98N_=E2=80=99 is meant to be an alias for =E2=80=98ngettex=
t=E2=80=99, so the above form
is invalid.

> And here is a problem...  Is it possible to compose a macro (e.g.,
> 'error*') with (exit 1) without touching the internals of
> 'define-output-macro'?

What about:

  (define-syntax-rule (leave args ...)
    (begin
      (error* args ...)
      (exit 1)))

Thanks,
Ludo=E2=80=99.