Thread: Beginner question about 'while'

Hello everyone, this is my first post here so I'll give a little background about myself. I know next to nothing about programming but I am attempting to teach myself C++ using lecture notes and assignments from MIT's CS department.

With that out of the way, here is my question. This program won't compile and I'm not sure why since I declared my variable 'N.' Do I need to declare it within the while loop? If so I don't understand why. Thanks!

Code:

#include <iostream>
using namespace std;


int main () {
        int N=0;
        cin >> N;


        while(N>0)
        {
                cout << N%5 == 0 && N%-1 ? N/5 : -1 << "\n";
        }
        return 0;
}

It'll compile at least, if you simply add parentheses here: (N%5 == 0 && N%-1 ? N/5 : -1) But I'm not sure if that's what you'd like it to do. I'm also a beginner.

Hmm interesting that worked, why is that?

The code after 'cout <<' is performing operations (ie checking if variables are equal ==, etc), so you need parentheses to let the compiler know the formatting so it knows exactly what you want between the <<s - else it might misinterpret things as other errors. If it was just single variables or basic math, of course you won't need parentheses.

Very helpful, much appreciated!

The parentheses are required because of operator precedence. If the statement were left alone, the bit shifting operator that the stream uses actually takes precedence over the ?: expression, so you have to use parens to get the order of operations correct. The compiler rarely gets confused.