unit_t init_behavior_impl(message_handler& x) { if (x) x = x.or_else(composable_behavior_base<Clauses>::make_callback()...); else x.assign(composable_behavior_base<Clauses>::make_callback()...); return unit; }
void assign_handler(Message, F&& f) { mh_.assign( Message(), std::forward< F >( f ) ); }