Ternary Operator

[agnea]

Hi guys!

I have this code, but I don't understand why it works...

#include <iostream>
using namespace std;

int main(){
	int a = 1;
	
	while (a <= 10){
		cout << (a % 2 ? "****":"++++++++++")<< endl;
		a++;
	}
	return 0;
}

The output is this...

****
++++++++++
****
++++++++++
****
++++++++++
****
++++++++++
****
++++++++++

Why this cout << (a % 2 ? "****":"++++++++++")<< endl; is true when a = 1, ?

thanks.

[chrisname]

It's to do with the nature of modulo/remainder'ing and of integer division.

To quote wikipedia:

When dividing 3 by 10, 3 is the remainder as we always take the front number as the remainder when the second number is of higher value.

So your program, seeing 2 as the larger number in 1 / 2 is deciding 1 is the remainder.

Try:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

#include <iostream> int main(){ int a = 1; while (a <= 10) { std::cout << "a = " << a << "\t" << a << " % 2 = " << a % 2 << "\n" << ((a % 2) ? "****" : "++++") << "\n"; a++; } std::cout << std::flush; return 0; }

a = 1 1 % 2 = 1 ++++ a = 2 2 % 2 = 0 **** a = 3 3 % 2 = 1 ++++ a = 4 4 % 2 = 0 **** a = 5 5 % 2 = 1 ++++ a = 6 6 % 2 = 0 **** a = 7 7 % 2 = 1 ++++ a = 8 8 % 2 = 0 **** a = 9 9 % 2 = 1 ++++ a = 10 10 % 2 = 0 ****

As for the others... well 3 / 2 == 1.5 . Integer division is truncating so you get 3 / 2 == 1. That leaves a remainder of 1.

[agnea]

Thanks!