Hello Codeforces Community,

Congratulations for the installation of C++20 automatic judge. A word of gratitude and appreciation is due to the Codeforces administration team for their endeavors to keep Codeforces up-to-date with the latest developments in C++.

The following program is an example for one of the new features introduced in C++20, __cpp_aggregate_paren_init.

#include <bits/stdc++.h>
using namespace std;

struct FourDPoint {
    int w, x, y, z;
    inline ostream& write(ostream& os) const {
        return os << '(' << w << ',' << x << ',' << y << ',' << z << ')'; }
    inline friend ostream& operator<<(ostream& os, const FourDPoint& p) {
        return p.write(os); } };

template<class value_type, size_t size>
struct Array: array<value_type,size> {
    inline ostream& write(ostream& os) const {
        os << '[' << this->front();
        for (size_t i = 1; i < size; ++i)
            os << ',' << this->at(i);
        return os << ']'; }
    inline friend ostream& operator<<(ostream& os, const Array& p) {
        return p.write(os); } };

int main() {
    const FourDPoint p(1,2,3,4);
    const Array<int,4> q({5,6,7,8});

    cout << "p = " << p << endl << "q = " << q << endl;

    return 0; }

The following is the expected output of this program.

This program produces a compilation error when compiled using GNU++17 9.2.0 compiler, but can be compiled successfully using GNU++20 11.2.0 compiler. The C++20 compiler translates that statement const FourDPoint p(1,2,3,4) into initializing the data members w, x, y, z of the constant object p to 1, 2, 3, and 4, respectively. Similarly, the compiler passes the initialization list {5,6,7,8} to the constructor of the base class array<int,4>, even though both classes FourDPoint and Array<int,4> do not have explicit class constructors.