[Boost-users] problem with boost units

the following small example fails to compile and points to error in assignment. For the life of me I can't figure why this should fail. Any help appreciated. Robert Ramey // include headers to implement output operations for quantities with units #include <iostream> #include #include int main(){ boost::units::si::volume fuel_capacity; fuel_capacity = 9.0f * boost::units::si::cubic_meters; ------------------^ std::cout << " " << fuel_capacity << "\n"; return 0; }