[Nix-dev] variable scope / recursion

[Kirill Elagin]

rec is the answer (this is something like let/letrec in Lisp, if you know
what I mean ;) ).

--
Кирилл Елагин


2012/7/6 Mathijs Kwik <mathijs at bluescreen303.nl>

> Hi all,
>
> I was reading this interesting piece of all-packages.nix
> (comments/whitespace removed):
>
>   applyGlobalOverrides = overrider:
>     let
>       overrides = overrider pkgsOrig //
>         (lib.optionalAttrs (pkgsOrig.stdenv ? overrides && crossSystem
> == null) (pkgsOrig.stdenv.overrides pkgsOrig));
>       pkgsOrig = pkgsFun pkgs {};
>       pkgs = pkgsFun pkgs overrides;
>     in pkgs;
>
> I'm familiar with tying-the-knot lazy trickery in haskell.
> As pkgsOrig uses pkgs (the final end result including overrides), and
> the overrider function gets passed pkgsOrig, I would expect the
> following to work:
>
>   packageOverrides = pkgs:
>     { foo = "string";
>       bar = pkgs.foo + " concatenation";
>     };
>
> However, it complains about foo missing.
> What am I missing?
>
> Thanks,
> Mathijs
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