[bug#36875] [PATCH] doc: Document the use of `program-file' for mcron jobs.

[Ludovic Courtès]

Hello!

Maxim Cournoyer <address@hidden> skribis:

> From 0fffed46b4899bf0485926399d3971a4b5e94408 Mon Sep 17 00:00:00 2001
> From: Maxim Cournoyer <address@hidden>
> Date: Thu, 1 Aug 2019 07:34:17 +0900
> Subject: [PATCH] doc: Document the use of `program-file' for mcron jobs.
>
> * doc/guix.texi (Scheduled Job Execution): Explain why using `program-file'
> for an mcron job can be necessary.  Add an example.

[...]

> +For more complex jobs defined in Scheme, it is safer to pass the job as a
> +script to mcron; otherwise, macros defined or imported with 
> @code{use-modules}
> +wouldn't expand correctly, as Guile requires macros to be strictly defined or
> +imported at the top level of a Guile module.  This can be achieved using the
> +@code{program-file} procedure from the @code{(guix gexp)} module, as shown in
> +the example below.

Macros are a very good example of the problem, but I wonder if it would
be clearer to simply write something like:

  For more complex jobs defined in Scheme where you need control over
  the top level, for instance to introduce a @code{use-modules} form, you
  can move your code to a separate program using the @code{program-file}
  procedure of the @code{(guix gexp)} module (@pxref{G-Expressions}).
  The example below illustrates that.

Anyway, your patch looks like a great improvement (and a funny example
:-)) so IMO you should push one version or another!

Thanks,
Ludo’.