anchor.diff:    };
   
     buildInputs = [ unzip libjpeg libtiff libpng proj openssl sqlite
  -    libspatialite poppler hdf4 qhull giflib expat ]
  +    libspatialite poppler hdf4 qhull giflib expat libxml2 ]
     ++ (with pythonPackages; [ python numpy wrapPython ])
     ++ stdenv.lib.optional stdenv.isDarwin libiconv
     ++ stdenv.lib.optionals netcdfSupport [ netcdf hdf5 curl ];
  
positive.code:     "--with-proj=${proj}" # optional
      "--with-geos=${geos}/bin/geos-config"# optional
      "--with-hdf4=${hdf4.dev}" # optional
      (if netcdfSupport then "--with-netcdf=${netcdf}" else "")
    ];
  
  
negative.code: { stdenv, fetchurl, fetchpatch, unzip, libjpeg, libtiff, zlib
  , postgresql, mysql, libgeotiff, pythonPackages, proj, geos, openssl
  , libpng, sqlite, libspatialite, poppler, hdf4, qhull, giflib, expat
  , libiconv, libxml2
  , netcdfSupport ? true, netcdf, hdf5, curl
  }:
  
  