From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: How can I use ()
Date: Tue, 16 Jan 2018 17:11:25 +0100
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In-Reply-To: <87h8rp25in.fsf@librem.i-did-not-set--mail-host-address--so-tickle-me>
	(Alex ter Weele's message of "Sat, 13 Jan 2018 08:32:48 -0600")
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To: Alex ter Weele <alex.ter.weele@gmail.com>
Cc: help-guix@gnu.org

Hi Alex,

Alex ter Weele <alex.ter.weele@gmail.com> skribis:

> Based on this, what I think I want to do is something like:
>
> ,enter-store-monad
> (build (list (gexp->script "test" (backup-home "alex"))))
>
> And then run the resulting script file. However, doing such gives the
> error:
>
> ERROR: In procedure string->utf8:
> ERROR: In procedure string->utf8: Wrong type argument in position 1 (expe=
cting string): #<procedure 327b030 at guix/gexp.scm:1128:2 (state)>

=E2=80=98gexp->script=E2=80=99 returns a =E2=80=9Cmonadic=E2=80=9D value, s=
o you need to =E2=80=9Cbind=E2=80=9D it with
=E2=80=98mlet=E2=80=99 or similar to actually access that value:

  (mlet %store-monad ((script (gexp->script =E2=80=A6)))
    (built-derivations (list script)))

Note that the whole result is again a monadic value.

Alternately, instead of fiddling at the REPL, you could do:

  guix gc -R $(guix system build config.scm) | grep mcron

then pick the right .drv from there, and run:

  guix build =E2=80=A6.drv

HTH!

Ludo=E2=80=99.