How do I put two increment statements in a C++ 'for' loop?

Question

I would like to increment two variables in a for-loop condition instead of one.

So something like:

for (int i = 0; i != 5; ++i and ++j)          


        

Answer 1

I agree with squelart. Incrementing two variables is bug prone, especially if you only test for one of them.

This is the readable way to do this:

int j = 0;
for(int i = 0; i < 5; ++i) {
    do_something(i, j);
    ++j;
}

For loops are meant for cases where your loop runs on one increasing/decreasing variable. For any other variable, change it in the loop.

If you need j to be tied to i, why not leave the original variable as is and add i?

for(int i = 0; i < 5; ++i) {
    do_something(i,a+i);
}

If your logic is more complex (for example, you need to actually monitor more than one variable), I'd use a while loop.