signed to unsigned (and vice versa)

[superbonzo]

if you cannot use boost or C++0x then you'll probably need to define a custom trait specialized for each signed/unsigned type

template <typename T> struct signed_t {};
template <typename T> struct unsigned_t {};

template <> struct signed_t<int> { typedef signed int type; };
template <> struct unsigned_t<int> { typedef unsigned int type; };

// ...

template<class T> void f( typename unsigned_t<T>::type v1, typename signed_t<T>::type v2 );

int main()
{
	f<int>(1,1);
}

of course, things get complicated if you want automatic type deduction ...