anchor.diff:  
     enableParallelBuilding = true;
   
  +  configurePhase = ''
  +    python build.py release
  +  '';
  +
     postPatch = ''
  -    cd src
       # Needed because the package tries to be too smart.
       export CC="$(which $CC)"
       export CXX="$(which $CXX)"
     '';
   
     installPhase = ''
  -    install -Dm755 bin/downward $out/libexec/fast-downward/downward
  -    cp -r ../translate $out/libexec/fast-downward/
  -    install -Dm755 ../../fast-downward.py $out/bin/fast-downward
  +    install -Dm755 builds/release/bin/downward $out/libexec/fast-downward/downward
  +    cp -r builds/release/bin/translate $out/libexec/fast-downward/
  +    install -Dm755 fast-downward.py $out/bin/fast-downward
       mkdir -p $out/${python3.sitePackages}
  -    cp -r ../../driver $out/${python3.sitePackages}
  +    cp -r driver $out/${python3.sitePackages}
   
       wrapPythonProgramsIn $out/bin "$out $pythonPath"
       wrapPythonProgramsIn $out/libexec/fast-downward/translate "$out $pythonPath"
  
positive.code:       echo "Moving $i to $dest"
        mv "$i" "$dest"
      done
    '';
  
    meta = with stdenv.lib; {
  
negative.code: { stdenv, lib, fetchhg, cmake, which, python3, osi, cplex }:
  
  stdenv.mkDerivation {
    version = "19.12";
    pname = "fast-downward";
  
    src = fetchhg {
      url = "http://hg.fast-downward.org/";
      rev = "41688a4f16b3";
      sha256 = "08m4k1mkx4sz7c2ab7xh7ip6b67zxv7kl68xrvwa83xw1yigqkna";
    };
  
    nativeBuildInputs = [ cmake which ];
  