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: , fetchurl
  , cmake
  , google-gflags ? null
  , glog ? null
  , runTests ? false
  }:
  
  
negative.code: 
    cmakeFlags = "
      -DEIGEN_INCLUDE_DIR=${eigen}/include/eigen3
    ";
  
    meta = with stdenv.lib; {
  