[Nix-dev] Re: May I remove the old python code?

[Andres Loeh]

Hi.

On Wed, Jan 7, 2009 at 7:32 PM, Ludovic Courtès <ludo at gnu.org> wrote:
> Hi,
>
> "Andres Loeh" <andres.loeh at googlemail.com> writes:
>
>> Ludo, while I have no idea about the actual implementation used for the new
>> python, I think that installing language libraries via nix-env and
>> solely relying
>> on ad-hoc composition in the user environment cannot in general work reliably.
>
> What makes you say so?

I always meant to reply to this, but I forgot. In the meantime, some
important points
have been discussed, in particular the fact that you essentially lose dependency
management in your profile if you rely on ad-hoc composition.

One other issue, I think, might not apply to an interpreted language
like python, but
it does apply to libs for compiled languages like Haskell that tend to
be binary-incompatible
between any two versions. If there actually is a build process
involved, you have to select
the compiler for which you want to build the library. If multiple
versions of a compiler are
around, and you still want to install via nix-env, you have to
multiply all libraries for all
compiler versions. A wrapper approach, on the other hand, makes this very easy.

Cheers,
  Andres