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

[Andres Loeh]

> What does "multiply all libraries for all compiler versions" mean?  In
> practice it boils down to applying a function to different compiler
> versions.

True.

> Think of kernel-dependent packages: we have `kernelPackagesFor', which
> takes a Linux kernel and returns a set of kernel-dependent packages, and
> then`configuration.nix' can specify a `kernelPackages' function.  The
> same approach could be used for Haskell or any other language.  The
> build farm admins can then choose to build whichever `kernelPackages'
> (or `ghcPackages', etc.) are important to them.

Something like that is certainly possible. But it won't guarantee that if
I install ghc-6.8.3 and one particular ghc package to my profile, it
will mean that the ghc package is available for that version of the
compiler.

Using a configuration.nix option to give a preference is one option,
directly writing out the composition is another. I slightly prefer the
latter (in general, actually), because a configuration option somehow
suggests that one user cannot have two versions of ghc installed at
the same time.

Actually, this leads to a question I have for quite some time: I'm
using several profiles for my user, and I hate having only one
~/.nixpkgs/config.nix
for all of them. Is there some easy way of switching to another
configuration file for a specific profile?

Cheers,
  Andres