Uh... maybe I didn't express clearly. It's currently defined as:
template <typename ColorBase, typename Color> get_color(ColorBase& cb, Color=Color())
I just want to know why not just take Color by the type, e.g.
template <typename Color, typename ColorBase> get_color(ColorBase& cb)
Sorry, I cannot comment on the this design decision. In case it really annoys you. You could just: template< typename Color, typename Color_Base > typename color_element_reference_type<Color_Base,Color>::type foo( Color_Base& p ) { return get_color( p, Color() ); } template< typename Color, typename Color_Base > typename color_element_const_reference_type<Color_Base,Color>::type foo( const Color_Base& p ) { return get_color( p, Color() ); } int main() { unsigned char ff = foo<red_t>( p ); return 0; } Hope this helps.
I'm trying the non-intrusive (adapted) approach to make it a Fusion Sequence, I'll back to here when done.
Code above could be rewritten as: fusion::at_key<red_t>(a) == fusion::at_key<red_t>(b)
Was Fusion around when gil was introduced? Christian