{ mkDerivation, attoparsec, base, bytestring, fetchurl }:
mkDerivation {
  pname = "hostname-validate";
  version = "1.0.0";
  src = fetchurl {
    url = "http://example.org/";
    sha256 = "abc";
  };
  libraryHaskellDepends = [ attoparsec base bytestring ];
  description = "Validate hostnames e.g. localhost or foo.co.uk.";
  license = stdenv.lib.licenses.bsd3;
}