I want to define operator * for a point type P. template <class T> class TPoint<T> { ... template <class U> TPoint<U> operator *(U t) const; ... }; template <class T> template <class U> TPoint<U> TPoint<T>::operator *(U t) const { return TPoint<U>((U)x()/t, (U)y()/t); } but I only want to define this for types for which boost::is_arithmetic<U> is true. This is because I also want to define operator * for an affine transformation template <class PT, class AT> inline Geomt::TPoint<AT> operator * (const Geomt::TPoint<PT>& pt, const AffHen<AT>& sAH) { Geomt::TPoint<AT> pout; sAH.Pt(pt.x, pt.y, pout.x, pout.y); return pout; } and this sometimes conflicts with the first definition. At the point of the first definition, type AffHen is unknown, so I can't branch there then using type traits. What I want to do is leave all argument types apart from arithmentic types undefined, to be available for later use. Is there a well known way to do this apart from making the affine transform the first argument? I wonder if boost type traits can help here. I know how to use type traits to enable compile time seperate procedures, but not how to use it to define a procedure for some type and not others. Craig Hicks