{ mkDerivation, base, fetchurl, pretty }:
mkDerivation {
  pname = "prettyclass";
  version = "1.0.0.0";
  src = fetchurl {
    url = "http://example.org/";
    sha256 = "abc";
  };
  libraryHaskellDepends = [ base pretty ];
  description = "Pretty printing class similar to Show";
  license = stdenv.lib.licenses.bsd3;
}