[boost] [mpl] and_<true_> returns false

The following snippet fails to compile (tested with 1.54.0 and trunk, several compilers), #include <boost/mpl/and.hpp> #include <boost/mpl/bool.hpp> #include <boost/mpl/or.hpp> int main() { using namespace boost::mpl; static_assert(and_<true_>::value, "U KID?"); //this one fires static_assert(or_<true_>::value, "U KID?"); //this one is ok } This issue actually showed up in a variadic template scenario. Is this a bug? I feel like I'm doing something really wrong... I guess one may not call `and_` with less than two arguments. If that's the case, it would be helpful if it would be impossible to instantiate it with a single argument. Regards, -- Agustín K-ballo Bergé.- http://talesofcpp.fusionfenix.com