From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ricardo Wurmus <rekado@elephly.net>
Subject: Re: use-modules in gexps
Date: Wed, 05 Feb 2020 16:18:12 +0100
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To: Ludovic =?utf-8?Q?Court=C3=A8s?= <ludo@gnu.org>
Cc: Guix-devel <guix-devel@gnu.org>


Ludovic Court=C3=A8s <ludo@gnu.org> writes:

>> I wondered if perhaps we could add a G-expression compiler for module
>> imports, so that instead of
>>
>> (with-imported-modules (source-module-closure '((my module)))
>>   #~(begin
>>      (use-modules (my module))
>>      =E2=80=A6))
>>
>> we would do
>>
>>   #~(begin
>>      #$(use-modules (my module))
>>      =E2=80=A6)
>>
>> which would have the effect of adding (my module) =E2=80=94 or the module
>> closure =E2=80=93 to the list of modules needed by the current G-express=
ion.
>
> I think the syntax should be different because #$/ungexp has a different
> meaning.  However, that would leave open the question of how to select
> the subset of the module=E2=80=99s closure you want to import, etc.
>
>> Can a G-expression compiler help accumulate state (e.g. by making
>> G-expressions values in the state monad) or can it only be compiled down
>> to a value at the current location?
>
> The latter.  What state would you want to accumulate?

When I wrote =E2=80=9Cstate=E2=80=9D I had the list of modules encountered =
in mind, so
that it would be possible to collect all marked instances of
=E2=80=9Cuse-module=E2=80=9D and hoist them to the top, in effect doing aut=
omatically
what is achieved manually by using =E2=80=9Cwith-imported-modules=E2=80=9D =
with a list
of modules.

--
Ricardo