 
            
            
            
            
                16 Jan
                
                    2007
                
            
            
                16 Jan
                
                '07
                
            
            
            
        
    
                5:44 a.m.
            
        Not impossible, just add another layer of indirection:
template<typename T1,typename T2> class quantity : public quantity_impl< typename mpl::if_< is_unit<T1>,T2,T1
::type, typename mpl::if_< is_unit<T1>,T1,T2 ::type {};
This is intriguing, but I'm not sure how one would enable a default template argument on just the value_type... Any ideas? Matthias