subtree(users/wpcarro): docking briefcase at '24f5a642'

git-subtree-dir: users/wpcarro
git-subtree-mainline: 464bbcb15c
git-subtree-split: 24f5a642af
Change-Id: I6105b3762b79126b3488359c95978cadb3efa789

users/wpcarro/buildHaskell/default.nix

@@ -0,0 +1,31 @@
+{ pkgs, ... }:
+
+{
+  # Create a nix-shell for Haskell development.
+  shell = { deps }: let
+    ghc = pkgs.haskellPackages.ghcWithPackages (hpkgs: deps hpkgs);
+  in pkgs.mkShell {
+    buildInputs = [ghc];
+  };
+
+  # Build a Haskell executable. This assumes a project directory with a
+  # top-level Main.hs.
+  # - `name`: You can find the result at ./result/$name
+  # - `srcs`: Will be passed to `srcs` field of `pkgs.stdenv.mkDerivation`.
+  # - `deps`: A function that accepts `hpkgs` and returns a list of Haskell
+  # - `ghcExtensions`: A list of strings representing the language extensions to
+  #   use.
+  program = { name, srcs, deps, ghcExtensions }: let
+    ghc = pkgs.haskellPackages.ghcWithPackages (hpkgs: deps hpkgs);
+  in pkgs.stdenv.mkDerivation {
+    name = name;
+    buildInputs = [];
+    srcs = srcs;
+    buildPhase = ''
+      ${ghc}/bin/ghc -Wall Main.hs ${pkgs.lib.concatMapStrings (x: "-X${x} ") ghcExtensions}
+    '';
+    installPhase = ''
+      mkdir -p $out && mv Main $out/${name}
+    '';
+  };
+}