anchor.diff:  }:
   
   let
  -
  -  buildMK = ''
  -    libraries/integer-gmp_CONFIGURE_OPTS += --configure-option=--with-gmp-libraries="${gmp}/lib"
  -    libraries/integer-gmp_CONFIGURE_OPTS += --configure-option=--with-gmp-includes="${gmp}/include"
  -    libraries/terminfo_CONFIGURE_OPTS += --configure-option=--with-curses-includes="${ncurses}/include"
  -    libraries/terminfo_CONFIGURE_OPTS += --configure-option=--with-curses-libraries="${ncurses}/lib"
  -    ${stdenv.lib.optionalString stdenv.isDarwin ''
  -      libraries/base_CONFIGURE_OPTS += --configure-option=--with-iconv-includes="${libiconv}/include"
  -      libraries/base_CONFIGURE_OPTS += --configure-option=--with-iconv-libraries="${libiconv}/lib"
  -    ''}
  -  '';
   
     docFixes = fetchurl {
       url = "https://downloads.haskell.org/~ghc/7.10.3/ghc-7.10.3a.patch";
  
positive.code:   configureFlags = [
      "--with-gcc=${stdenv.cc}/bin/cc"
      "--with-gmp-includes=${gmp}/include" "--with-gmp-libraries=${gmp}/lib"
    ];
  
    # required, because otherwise all symbols from HSffi.o are stripped, and
  
negative.code:   enableParallelBuilding = true;
  
    preConfigure = ''
      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}"
  