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Haskell in Nixpkgs/NixOS

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For discussions and questions about Haskell with Nix, cabal2nix and haskellPackages in nixpkgs | Current Docs: https://haskell4nix.readthedocs.io/142 Servers

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21 Jul 2025
@magic_rb:matrix.redalder.orgmagic_rbthe monkey forgot to use a variable he declared10:21:57
@alex:tunstall.xyzAlex
In reply to @magic_rb:matrix.redalder.org
im benchmarking a thing i wrote and im making a nix package out of a cabal file using cabal2nix, however if i change the source cabal file and remove -fllvm, -O2, or -fexpose-all-unfoldings the performance measurements dont seem to change even though im positive they should. Is nixpkgs overwriting my flags somehow?
If you're using a profiling build, beware of automatic cost centres (IIRC enabled by default in cabal).
10:37:54
@magic_rb:matrix.redalder.orgmagic_rb
In reply to @alex:tunstall.xyz
If you're using a profiling build, beware of automatic cost centres (IIRC enabled by default in cabal).
Nope, i know about those
10:49:29
22 Jul 2025
@maralorn:maralorn.demaralornDoes anyone here grok/has used the useIntermediates stuff? I have one question: Can it reuse the intermediates of a previous build even when that build had other dependency hashes on the nix side? The argument was that cabal-install does not always have to recompile your project when you modify your nix shell. And the reusing is probably happening based on some cabal level hashing?15:02:25
@sternenseemann:systemli.orgsterniWell development shell is out anyways since that's Setup.hs which cabal-install won't be able to reuse in any shape or form I think18:57:16
@maralorn:maralorn.demaralornAre you sure? Maybe the components are similar enough? I mean they have been compiled with the same ghc. Isn’t it basically a dir with .hie and object files in both cases?20:55:26
24 Jul 2025
@keetonbrewster:matrix.orgKeeton Brewster joined the room.00:12:02
@keetonbrewster:matrix.orgKeeton BrewsterHi everyone, is there a Haskell specific Nix beginner guide out there? 00:14:32
@keypusher:matrix.orgkeypusherI think it's a bit fragmented depending on your needs / approach as can be seen in this thread https://www.reddit.com/r/haskell/comments/1cqfboq/latest_guidance_on_using_haskell_with_nix/ . Some years ago my searches often ended up here https://haskell4nix.readthedocs.io/ 00:45:35

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