Partial template specialization based on “signed-ness” of integer type?

Question

Given:

template
inline bool f( T n ) {
  return n >= 0 && n <= 100;
}   

When used with an unsigned

Answer 1

You can take advantage of the wrap-around behavior of unsigned integers.

template struct bool_ { };

template
inline bool f( T n, bool_ ) {
  return n >= 0 && n <= 100;
}

template
inline bool f( T n, bool_ ) {
  return n <= 100;
}

template
inline bool f( T n ) {
  return f(n, bool_<(static_cast(-1) > 0)>());
}   

It's important not to say >= 0, to avoid a warning again. The following appears to trick GCC too

template
inline bool f( T n ) {
  return (n == 0 || n > 0) && n <= 100;
}