In this article, we are going to review two new features of C++23. Now the language allows the call operator (operator()) and the subscription operator (operator[]) to be static.

C++23: static operator() and static operator[]

By Sandor Dargo

From the article:

static operator()

As we saw earlier in our big C++ algorithms tutorial, function objects are extensively used in the standard library to customise the behaviour of several functions. With the introduction of ranges in C++20 (and of earlier non-standard libraries), the usage of function objects became even more widespread.

Many function objects are extremely simple. Let’s take an implementation of isEven.

auto isEven = [](int i) {return i % 2 == 0;};