I think paul Fultz wrote:

Actually, you could just take the optional_traits as the first parameter. So you define optional<T> or optional<optional_traits<my_traits<T> > >. Then optional would be specialized for optional_traits that will get the user-defined traits.

That new optional might break old code: template<typename T> void print(const optional<T>& o){ if(o){ T copy=*o; std::cout<<copy; } } That copy is going to be a optional_traits<>. My method would also force you to add traits to the signature, but at least you wouldn't need to write two specializations: template<typename T,typename Traits> void print(const optional_with_traits<T, Traits >& o); Se have to ask ourselves if configuration is worth it. I think sometimes you don't find that out until it's too late and someone wants a option. Things I can think of making configurable: * bool type - a word might be faster on risk machines * use_trivial_destruction - there might be a case for overridding this * use_trivial_copy - cann't see a case for overriding this * bool_first * alignment - maybe 4 byte alignment is legal but 8 byte is faster * enable_assertions Chris