Increment operator in C

Question

I tried the following code snippet:

void main()
{
    int x = 1,y = 1,z = 1;
    ++x || ++y && ++z;
    printf("x = %d\ny = %d\nz = %d\n",x,y,z);
}

The output I expected was:

x = 2
y = 2
z = 2

But I am getting the output:

x = 2
y = 1
z = 1

What is the reason for this?

Answer 1

This is because of short-circuiting.

http://en.wikipedia.org/wiki/Short-circuit_evaluation

When this is evaluated:

++x || ++y && ++z;

The first part ++x already determines the value of the entire expression. So the ++y && ++z is not executed at all. So the side-effects of ++y and ++z are not invoked.

Answer 2

The result of ++x is nonzero, so evaluates to true, so short-circuits the || operator. ++y && ++z is not executed.