anchor.diff:      "--with-pythia=${pythia}"
     ];
   
  -  postInstall = stdenv.lib.optionalString stdenv.isDarwin ''
  +  postInstall = if stdenv.isDarwin then ''
       install_name_tool -add_rpath ${pythia}/lib "$out"/bin/run-pythia
  +  '' else ''
  +    wrapProgram $out/bin/run-pythia \
  +      --prefix LD_LIBRARY_PATH : "${pythia}/lib"
     '';
   
     enableParallelBuilding = true;
  
positive.code: { stdenv, fetchurl, boost, hepmc, lhapdf, pythia }:
  
  stdenv.mkDerivation rec {
    name = "sacrifice-${version}";
  
negative.code:   };
  
    buildInputs = [ boost hepmc lhapdf pythia ];
    nativeBuildInputs = [ makeWrapper ];
  
    patches = [
      ./compat.patch
  