Question

Which of the following is a logical unary functor?

(a) logical_or<T> f;

(b) logical_and<T> f;

(c) logical_not<T> f;

(d) negate<T> f;

The question was asked during an online exam.

Origin of the question is Functors in chapter Algorithms, Objects & Iterators in C++ of C++

Answer 1

The correct choice is (c) logical_not<T> f;

To explain I would say: logical_and and logical_or requires two arguments to act upon whereas negate and logical_not requires only one argument but negate also produces non-logical results like negate of a number, therefore, it is not logical hence logical_not<T> f; is an only logical functor.