{ mkDerivation, base, containers, fetchurl, mtl }:
mkDerivation {
  pname = "tree-fun";
  version = "0.8.1.0";
  src = fetchurl {
    url = "http://example.org/";
    sha256 = "abc";
  };
  libraryHaskellDepends = [ base containers mtl ];
  description = "Library for functions pertaining to tree exploration and manipulation";
  license = stdenv.lib.licenses.gpl3;
}