If you overload operator== do you also need to overload operator!=?

Question

I am using the BOOST_STRONG_TYPEDEF macro, which creates a class that overloads operator==. I'm wondering if I need to overload operator!= as well?

Answer 1

Answer: no!

The reason (that I didn't notice at first) is that BOOST_STRONG_TYPEDEF uses Boost operators (http://www.boost.org/doc/libs/1_38_0/libs/utility/operators.htm), specifically totally_ordered1 and totally_ordered2. So the less than and equality comparison operators are implemented for you.