Get the signed/unsigned variant of an integer template parameter without explicit traits

The answer is in <type_traits>

For determining the signed-ness of a type use std::is_signed and std::is_unsigned.

For adding/removing signed-ness, there is std::make_signed and std::make_unsigned.

If you can't or don't want to depend on TR1/C++0x features, Boost.TypeTraits also offers you make_unsigned<> et al.