Haskell

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Introduction

Nix recipes for Haskellers aims to get a beginner comfortable managing simple Haskell programs and projects using Nix.

Scripting

Here's an example using nix-shell to get a redistributable Haskell script that you can run on any Nix system with `./my-script.hs`:

#!/usr/bin/env nix-shell
#!nix-shell --pure -i runghc -p "haskellPackages.ghcWithPackages (pkgs: [ pkgs.turtle ])"

main = do
  # do stuff
  putStrLn "Hello world from a distributable Haskell script!"

FAQ

Limitations

When using cabal2nix, Nix does not pull a cabal package by respecting the constraint specified in the cabal file (see example). Issue is discussed here. You should be using `callCabal2nix` anyway.

IFD and Haskell

callCabal2nix, which is implicitly used for building Haskell projects, uses IFD.[1][2]. This means that since IFD is disabled by default in certain nix commands,[3] the following commands will be broken for Haskell projects whose flake output specifies multiple system attributes:

  • nix flake show
  • nix flake check