C++ 用于使用逗号运算符的多个控制语句

Question

How does comma operator if it is used in a 'for loop' for writing multiple control statements? i tried

#include <iostream>

using namespace std;

int main() {
        for (int x = 0, y = 0; x < 3, y < 4; ++x, ++y) {
                cout << x << " " << y << endl;
        }
        return 0;
}

and it seems like only the last expression is evaluated. Ty

Answer 1

This is how comma operator works. Its 1st operand x < 3 is evaluated, then the result is discarded; then the 2nd operand y < 4 is evaluated and the value is returned as the return value of the comma operator. x < 3 has not any effects here.

You might want to use operator&& or operator|| for this case, eg x < 3 && y < 4 or x < 3 || y < 4 x < 3 || y < 4 based on your intent.