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:       libraries/base_CONFIGURE_OPTS += --configure-option=--with-iconv-libraries="${libiconv}/lib"
      ''}
    '';
  
  in
  
  
negative.code: { stdenv, fetchurl, fetchpatch, ghc, perl, gmp, ncurses, libiconv }:
  
  let
  
  