anchor.diff:  
   let
     version = "1.10.0";
  -
  -  # glog currently doesn't build on darwin
  -  # Issue: https://code.google.com/p/google-glog/issues/detail?id=121
  -  useGlog = glog != null && !stdenv.isDarwin;
  -
   in
   stdenv.mkDerivation {
     name = "ceres-solver-${version}";
  
positive.code:     sha256 = "20bb5db05c3e3e14a4062e2cf2b0742d2653359549ecded3e0653104ef3deb17";
    };
  
    buildInputs = [ cmake ]
      ++ stdenv.lib.optional useGlog glog
      ++ stdenv.lib.optional (google-gflags != null) google-gflags;
  
    inherit eigen;
  
negative.code: , fetchurl
  , cmake
  , google-gflags ? null
  , glog
  , runTests ? false
  }:
  
  