anchor.diff:        spectrophotometry.
       '';
       license = stdenv.lib.licenses.gpl2;
  -    platforms = stdenv.lib.platforms.linux;
  +    platforms = with stdenv.lib.platforms; linux ++ darwin;
       maintainers = [ stdenv.lib.maintainers.cge ];
     };
   }
  
positive.code:   zlibSupport ? true, zlib ? null,
    libuniqueSupport ? true, libunique ? null,
    libpngSupport ? true, libpng ? null,
    openglSupport ? true
  }:
  
  assert openexrSupport -> openexr != null;
  
negative.code:   
    buildInputs = with stdenv.lib;
      [ gtk2 fftw ] ++
      optional openglSupport gnome2.gtkglext ++
      optional openexrSupport openexr ++
      optional libXmuSupport xorg.libXmu ++
      optional fitsSupport cfitsio ++
  