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To remove the additional latency overhead of a nix-shell, add GHC to <code>environment.systemPackages</code> and call <code>runghc</code> in the shebang.<syntaxhighlight lang="nix">
To remove the additional latency overhead of a nix-shell, add GHC to <code>environment.systemPackages</code> and call <code>runghc</code> in the shebang.<syntaxhighlight lang="nix">
  environment.systemPackages = with pkgs; [
environment.systemPackages = with pkgs; [
    ...
  ...
    (ghc.withPackages (hsPkgs: with hsPkgs; [
  (ghc.withPackages (hsPkgs: with hsPkgs; [
      turtle      # Faster startup time with all external shell commands
    turtle      # Faster startup time with all external shell commands
      shh        # Piping operators and other goodies
    shh        # Piping operators and other goodies
      shh-extras  # Try shh as an interactive shell
    shh-extras  # Try shh as an interactive shell
      ...        # ...anything else you want!
    ...        # ...anything else you want!
    ])
  ])
  ];  
];
</syntaxhighlight>Here's a basic example using the Shh module rather than Turtle, so it can use the pipe operator:<syntaxhighlight lang="haskell">
</syntaxhighlight>Here's a basic example using the Shh module rather than Turtle, so it can use the pipe operator:<syntaxhighlight lang="haskell">
#!/usr/bin/env runghc
#!/usr/bin/env runghc
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For instance you can define your various projects in subfolders <code>./frontend</code> and <code>./backend</code> (you can use cabal init to create the content in each folder), then create a file <code>cabal.project</code> containing:
For instance you can define your various projects in subfolders <code>./frontend</code> and <code>./backend</code> (you can use cabal init to create the content in each folder), then create a file <code>cabal.project</code> containing:


{{file|cabal.project|nix|
{{file|cabal.project|haskell|
<nowiki>
<nowiki>
packages:
packages:
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* [https://haskell.nixos.asia/dependency Overriding dependencies in a haskell-flake]
* [https://haskell.nixos.asia/dependency Overriding dependencies in a haskell-flake]


* [https://flake.parts/options/haskell-flake haskell-flake haskell-flake options reference]
* [https://flake.parts/options/haskell-flake haskell-flake options reference]


== Overrides ==
== Overrides ==