anchor.diff:      hlint
       tasty
       tasty-hunit
  +
  +    # DB
  +    postgrest
     ]);
   in
   pkgs.stdenv.mkDerivation {
  
positive.code:   buildInputs = [
      cabal
      ghc
    ];
    shellHook = "eval $(egrep ^export ${ghc}/bin/ghc)";
  }
  
negative.code: { nixpkgs ? import <nixpkgs> {}, compiler ? "ghc7102" }:
  let
    inherit (nixpkgs) pkgs;
  
    # Please note that Sqitch requires PosgreSQL 9.4 which is present in
    # configuration.nix
    sqitch = pkgs.sqitchPg;
  
    # Haskell.
    cabal = pkgs.cabal-install;
    ghc = pkgs.haskell.packages.${compiler}.ghcWithPackages (ps: with ps; [
      http-conduit
  