In a type trait, why do people use enum rather than static const for the value?

Question

For example, this is how I would write it, and it compiles and works just fine:

template struct is_pointer {
  static const bool valu         


        

Answer 1

Yes you are correct: enum { value = true }; doesn't occupy any memory.

Furthermore, prior to C++11 it was pretty much the only way of achieving this: static const bool value = true; is only legal in a class definition from C++11 onwards. Although a constexpr might be preferred.