C++ Quiz

Difficulty:

According to the C++23 standard, what is the output of this program?

#include <iostream>

int main() {
    int a[] = <%1%>;
    std::cout << a<:0:>;
}

Hint

C++ provides alternatives for certain tokens.

Reveal answer

Explanation

C++ provides alternative tokens for some punctuators. The two weird lines are exactly equivalent to

int a[] = {1};
std::cout << a[0];

§[lex.digraph]¶1 in the C++ standard explains this:

Alternative token representations are provided for some operators and punctuators.

In all respects of the language, each alternative token behaves the same, respectively, as its primary token, except for its spelling.

Then, a table of alternative tokens is provided, which includes