foo.nix

{ nixpkgs ? import <nixpkgs> {} }:
with nixpkgs;
let
  hpkgs = pkgs.haskell.packages.ghc843;
  nlopt-new = hpkgs.mkDerivation {
    pname = "nlopt-haskell";
    version = "0.1.2.0";
    src = fetchFromGitHub {
      owner = "peddie";
      repo = "nlopt-haskell";
      rev = "dd8c88334a91e51598beecfd02165a1810890c43";
      sha256 = "1bmb53a3k4scr8higwihz2nrf1r4041sxxr1gg8xfajzy03n0qmd";
    };
    libraryHaskellDepends = (with hpkgs; [base vector ]);
    testHaskellDepends = (with hpkgs;  [ base vector ]);
    librarySystemDepends = [ pkgs.nlopt ];
    testSystemDepends = [ pkgs.nlopt ];
    homepage = "https://github.com/peddie/nlopt-haskell";
    description = "Low-level bindings to the NLOPT optimization library";
    license = stdenv.lib.licenses.bsd3.fullName;
    configureFlags = ["-flink-nlopt-cxx"];
  };
  hmatrix-nlopt-new = hpkgs.mkDerivation {
    pname = "hmatrix-nlopt";
    version = "0.1.2.0";
    src = fetchFromGitHub {
      owner = "peddie";
      repo = "hmatrix-nlopt";
      rev = "e13a471599d5fca318d4bfc9417d1156bea3bb5";
      sha256 = "01bn12d90f8gfrw2fgq2yrpwh8p8wz0w922vvh716vjn2g647x5q";
    };
    libraryHaskellDepends = (with hpkgs; [base hmatrix nlopt-new vector ]);
    testHaskellDepends = (with hpkgs;  [ base doctest ]);
    homepage = "https://github.com/peddie/hmatrix-nlopt";
    description = "Interface HMatrix with the NLOPT minimizer";
    license = stdenv.lib.licenses.bsd3.fullName;
  };
  ghc = hpkgs.ghcWithPackages (ps: with ps; [
    hmatrix-nlopt-new
    hmpfr
    hmatrix-gsl
  ]);
in
pkgs.stdenv.mkDerivation {
  name = "my-haskell-env-0";
  buildInputs = [ ghc ];
  shellHook = "eval $(egrep ^export ${ghc}/bin/ghc)";
}