anchor.diff: -{stdenv, fetchurl, ghc, perl, gmp, ncurses}:
  +{stdenv, fetchurl, ghc, perl, gmp, ncurses, darwinInstallNameToolUtility}:
   
   stdenv.mkDerivation rec {
     version = "7.0.2";
  
positive.code: 
    preConfigure = ''
      echo "${buildMK}" > mk/build.mk
    '';
  
    configureFlags=[
  
negative.code:     sha256 = "f0551f1af2f008a8a14a888b70c0557e00dd04f9ae309ac91897306cd04a6668";
    };
  
    buildInputs = [ghc perl gmp ncurses] ++
      (if stdenv.isDarwin then [darwinInstallNameToolUtility] else []);
  
    buildMK = ''
      libraries/integer-gmp_CONFIGURE_OPTS += --configure-option=--with-gmp-libraries="${gmp}/lib"
  