dhall-nix

Dhall to Nix compiler

Monthly Downloads: 121

Programming language: Haskell

License: BSD 3-clause "New" or "Revised" License

Tags: Compiler     Dhall    

README

dhall-nix 1.1.6

This dhall-nix package provides a Dhall to Nix compiler. You can use this compiler to program Nix using the Dhall language. This package targets people who wish Nix had a type system.

Quick start

If you have Nix installed then you can build and run this package using:

$ nix-build -A dhall-nix release.nix
$ result/bin/dhall-to-nix <<< "λ(x : Bool) → x == False"
x: x == false
$ result/bin/dhall-to-nix <<< "{ foo = 1, bar = True }"
{ bar = true; foo = 1; }
$ result/bin/dhall-to-nix <<< "< Left = 2 | Right : Natural >"
{ Left, Right }: Left 2

However, this package is also designed to be used directly from Nix. You can use the following dhallToNix utility to translate Dhall source code to the corresponding Nix expression directly within Nix:

dhallToNix = code :
  let
    file = builtins.toFile "dhall-expr" code;

    drv = pkgs.stdenv.mkDerivation {
      name = "dhall-expr-as-nix";

      buildCommand = ''
        dhall-to-nix <<< "${file}" > $out
      '';

      buildInputs = [ pkgs.haskellPackages.dhall-nix ];
    };
  in
    import "${drv}";

The above dhallToNix utility is now in nixpkgs so you can use pkgs.dhallToNix to transform Dhall expressions to Nix expressions

Development status

I don't expect this library to change unless:

• ... the Dhall language changes, which is possible but not very likely
• ... there are bugs, but the test suite in [release.nix](./release.nix) should protect against this

License (BSD 3-clause)

Copyright (c) 2017 Gabriel Gonzalez
All rights reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:
    * Redistributions of source code must retain the above copyright notice,
      this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright notice,
      this list of conditions and the following disclaimer in the documentation
      and/or other materials provided with the distribution.
    * Neither the name of Gabriel Gonzalez nor the names of other contributors
      may be used to endorse or promote products derived from this software
      without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.