Shouldnt this work?: #include <boost/numeric/interval.hpp> int main() { boost::numeric::interval<double> v(.5); cos(v); } ------------------ I get this error in VC7.1: c:\boost\include\boost-1_33_1\boost\numeric\interval\transc.hpp(73) : error C2039: 'cos_down' : is not a member of 'boost::numeric::interval_lib::rounded_math<double>' c:\boost\include\boost-1_33_1\boost\numeric\interval\hw_rounding.hpp(53) : see declaration of 'boost::numeric::interval_lib::rounded_math<double>' e:\Projects\Test\test.cpp(6) : see reference to function template instantiation 'boost::numeric::interval<T> boost::numeric::cos<double,boost::numeric::interval_lib::default_policies<T>::type>(const boost::numeric::interval<T> &)' being compiled with [ T=double ] c:\boost\include\boost-1_33_1\boost\numeric\interval\transc.hpp(73) : error C2039: 'cos_up' : is not a member of 'boost::numeric::interval_lib::rounded_math<double>' c:\boost\include\boost-1_33_1\boost\numeric\interval\hw_rounding.hpp(53) : see declaration of 'boost::numeric::interval_lib::rounded_math<double>' c:\boost\include\boost-1_33_1\boost\numeric\interval\transc.hpp(75) : error C2039: 'cos_up' : is not a member of 'boost::numeric::interval_lib::rounded_math<double>' c:\boost\include\boost-1_33_1\boost\numeric\interval\hw_rounding.hpp(53) : see declaration of 'boost::numeric::interval_lib::rounded_math<double>' regards Andy Little