It's as useful (or not) as you find this: https://cppreference.com/w/cpp/utility/functional/not_fn.html https://cppreference.com/w/cpp/utility/functional/not_f

It's as useful (or not) as you find this: https://cppreference.com/w/cpp/utility/functional/not_fn.html https://cppreference.com/w/cpp/utility/functional/not_fn.htm... If you don't see any value in that, you wouldn't see any value in the similar `flip` function or other combinators.