From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: Reproducible environments
Date: Wed, 07 Oct 2015 14:11:51 +0200
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	(Konrad Hinsen's message of "Tue, 6 Oct 2015 18:59:44 +0200")
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To: Konrad Hinsen <konrad.hinsen@fastmail.net>
Cc: guix-devel@gnu.org

Konrad Hinsen <konrad.hinsen@fastmail.net> skribis:

> Here's an example (a simplified version of the real situation that motiva=
ted
> me to check out Guix):
>
>    - I need to use Program X that depends on libraries A and B.
>    - The current versions are A-1.1 and B-42.0.1.
>    - X requires "1.0 or later" for A but "41.*"  for B, because
>      version 42.* of B is not fully backwards compatible.
>
> If there's no Guix commit that has both A and B in the required
> version range, then the easiest way to get what I need is to use an
> older Guix commit for installing B than I use for A.

That works if you use =E2=80=98guix package -i=E2=80=99 to incrementally bu=
ild the
profile, using different Guix commits; but it prevents you from using
the declarative =E2=80=98--manifest=E2=80=99 approach.

> In fact, the only other alternative I see is to add a package definition
> for the old version of B to a later Guix commit. That's likely to be
> much more difficult.

It depends, but not necessarily.  It=E2=80=99s particularly easy to maintain
different versions of leaf packages, as shown in Figure 4 of the paper.

Ludo=E2=80=99.