Hi, Let's we have using boost::lambda::_1; typedef boost::remove_reference<decltype(_1)>::type _1_type; Then, decltype(_1(1)) (and std::result_of<_1_type(int)>::type) is 'int const&', but boost::tr1_result_of<_1_type(int)>::type is 'int&". Is this a bug? Regards, Michel