[Nix-dev] Developing with older packages

[Vladimír Čunát]

On 09/08/2014 08:12 PM, Richard Wallace wrote:
> One thing that surprised me about nix when I started using it is that
> there isn't a way to say, "I need package X with version Y".  Instead,
> you have to resort to having multiple definitions of the package with
> different package names for different versions.  This seems a bit hacky
> to me.

When you change version, you have to change the download hash, and often 
also some other things like dependencies or patches. As many things may 
be different, having a special attribute name is a flexible convention.

In nixpkgs we do not maintain old versions unless there is a good reason 
to do so. For those cases, the language offers many ways of sharing code 
among multiple versions, although some of those techniques were disputed 
a lot and disapproved.


Vladimir


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