Why is inequality tested as (!(a==b)) in a lot of C++ standard library code?

Question

This is the code from the C++ standard library remove code. Why is inequality tested as if (!(*first == val)) instead of if (*first != val)

Answer 1

Because this means the only requirement on T is to implement an operator==. You could require T to have an operator!= but the general idea here is that you should put as little burden on the user of the template as possible and other templates do need operator==.