Hi there, I cannot understand why the code below gives me a static assertion. As far as I know I use a very common technique to to extract a type from templated class using specialization over this class. #include <boost/assert.hpp> #include <boost/type_traits/is_same.hpp> #include <boost/gil/gil_all.hpp> namespace boost { namespace gil { template< typename T > struct bit_field_type{ typedef T type; }; template< typename BitField, typename ChannelBitSizes, typename Layout, bool IsMutable > struct bit_field_type< bit_aligned_pixel_reference< BitField , ChannelBitSizes , Layout , IsMutable > > { typedef BitField type; }; } // namespace gil } // namespace boost int main(int argc, char* argv[]) { typedef boost::gil::bit_aligned_image1_type< 1, boost::gil::gray_layout_t >::type gray1_image_t; typedef gray1_image_t::view_t::reference ref; typedef boost::gil::bit_field_type< ref >::type bit_field_t; BOOST_STATIC_ASSERT(( boost::is_same< bit_field_t, unsigned char >::value )); return 0; } The type for gray1_image_t::view_t::reference is the following: boost::gil::bit_aligned_pixel_reference< unsigned char, boost::mpl::vector1_c< unsigned int, 1 > , boost::gil::layout< boost::mpl::vector1< boost::gil::gray_color_t >, boost::mpl::range_c< int, 0, 1> > , 1 > Can somebody tell what wrong. I have been staring at this for too long. I'm using MS Visual Studio 9 and 10. Thanks in advance, Christian