Can anyone help me insert a compile time check on the validity ( > 0) of std::numeric_limits<FPT>::epsilon(). In this code (in floating_point_comparison.hpp) template<typename FPT> bool operator()(FPT left, FPT right) { // ((left-right)/left) / epsilon) BOOST_STATIC_ASSERT(std::numeric_limits<FPT>::is_specialized); // OK. BOOST_STATIC_ASSERT(numeric_limits<FPT>::is_iec559); // OK BOOST_STATIC_ASSERT((DBL_EPSILON > 0)); // OK too. BOOST_STATIC_ASSERT(DBL_EPSILON); // OK, but I am trying to check for UDT FPT BOOST_STATIC_ASSERT(numeric_limits<FPT>::epsilon()); // Fails to compile BOOST_STATIC_ASSERT(numeric_limits<FPT>::epsilon() > (FPT)0); // as does this. // error C2975: 'x' : invalid template argument for 'boost::STATIC_ASSERTION_FAILURE', expected compile-time constant expression (I could just return false but this would help the user much). return ...; } epsilon should be a constant known at compile time? But is the compile unable to know this? Other suggestions on how to achieve a compile-time warning here? Thanks Paul -- Paul A Bristow Prizet Farmhouse, Kendal, Cumbria UK LA8 8AB Phone and SMS text +44 1539 561830, Mobile and SMS text +44 7714 330204 mailto: pbristow@hetp.u-net.com http://www.hetp.u-net.com/index.html http://www.hetp.u-net.com/Paul%20A%20Bristow%20info.html