Question

I wrote this very simple program:

    #include <iostream>

using namespace std;

int main()
{
    int x = 0;

    cout << x++<<endl;
    cout<<++x<<endl;
    int y = 0;

    cout<<y--<<endl;
    cout<<--y<<endl;
    return 0;
}

and this is what i got when i ran it:

0

2

0

-2

i use code::blocks for writing the program and my operating system is Ubuntu 12.10.
how should i fix my program so i will see 0 1 0 -1 instead?

Answer 1

You need to understand the concepts of post increment(decrement) and pre increment(decrement).

Post increment

cout << x++<<endl;

You can understand this line as "Return the value of x" + "increment the value of x". I.e The return value is before the increment.

So return 0 and increase the value of x to 1.

Pre increment

cout<<++x<<endl;

This is the opposite – the incremented value is returned.

So increase the value of x to 2 and return 2.