The following code example is taken from the book
C++ Templates - The Complete Guide
by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002
© Copyright David Vandevoorde and Nicolai M. Josuttis 2002
// primary template for type promotion
template<typename T1, typename T2>
class Promotion {
public:
typedef typename
IfThenElse<(sizeof(T1)>sizeof(T2)),
T1,
typename IfThenElse<(sizeof(T1)<sizeof(T2)),
T2,
void
>::ResultT
>::ResultT ResultT;
};