anchor.diff:    configureFlags = [
       "--with-gcc=${stdenv.cc}/bin/cc"
       "--with-gmp-includes=${gmp}/include" "--with-gmp-libraries=${gmp}/lib"
  +    "--with-curses-includes=${ncurses}/include" "--with-curses-libraries=${ncurses}/lib"
  +  ] ++ stdenv.lib.optional stdenv.isDarwin [
  +    "--with-iconv-includes=${libiconv}/include" "--with-iconv-libraries=${libiconv}/lib"
     ];
   
     # required, because otherwise all symbols from HSffi.o are stripped, and
  
positive.code:   enableParallelBuilding = true;
  
    preConfigure = ''
      echo >mk/build.mk "${buildMK}"
      sed -i -e 's|-isysroot /Developer/SDKs/MacOSX10.5.sdk||' configure
    '' + stdenv.lib.optionalString (!stdenv.isDarwin) ''
      export NIX_LDFLAGS="$NIX_LDFLAGS -rpath $out/lib/ghc-${version}"
  
negative.code: }:
  
  let
  
    docFixes = fetchurl {
      url = "https://downloads.haskell.org/~ghc/7.10.3/ghc-7.10.3a.patch";
  