anchor.diff:  
     enableParallelBuilding = true;
   
  -  # We patch Cabal for GHCJS. See: https://github.com/haskell/cabal/issues/2454
  +  postPatch = ''
  +    pushd libraries/Cabal
  +    patch -p1 < ${cabalPatch}
  +    popd
  +  '';
  +
     preConfigure = ''
  -    sed -i 's/HcPkg.useSingleFileDb = .*/HcPkg.useSingleFileDb = False/' libraries/Cabal/Cabal/Distribution/Simple/GHCJS.hs
       echo >mk/build.mk "${buildMK}"
       sed -i -e 's|-isysroot /Developer/SDKs/MacOSX10.5.sdk||' configure
     '' + stdenv.lib.optionalString (!stdenv.isDarwin) ''
  
positive.code: { stdenv, fetchurl, ghc, perl, gmp, ncurses, libiconv }:
  
  let
  
  
negative.code:       libraries/base_CONFIGURE_OPTS += --configure-option=--with-iconv-libraries="${libiconv}/lib"
      ''}
    '';
  
    # We patch Cabal for GHCJS. See: https://github.com/haskell/cabal/issues/2454
    # This should be removed when GHC includes Cabal > 1.22.2.0
    cabalPatch = fetchpatch {
      url = https://github.com/haskell/cabal/commit/f11b7c858bb25be78b81413c69648c87c446859e.patch;
      sha256 = "1z56yyc7lgc78g847qf19f5n1yk054pzlnc2i178dpsj0mgjppyb";
    };
  
  in
  
  