Question

Consider this loop:

int[] myArray = new int[10];

int myIndex = 0;
for (int i = 0; i < 10; i++)
{
    myArray[myIndex++] = myIndex;
    Console.WriteLine(myArray[i]);
}

This yields:

1
2
3
...

Because myIndex is post-incremented, and the right side is evaluated first, shouldn’t the array index 0 contain 0?

Can someone explain this order-of-operations misunderstanding for me?

Answer 1

The right side isn’t necessarily evaluated first. Similar to:

foo.Bar.Baz = a + b;

In the above code, foo.Bar is evaluated first, then a + b, then the set_Baz method is called to set the Baz property to whatever is evaluated on the right.

So in your code, if you break it into pieces, it looks like this:

var index = i;
// post-incremented in the original code means this comes after the line above,
// but not after the line below it.
i += 1; 
myArray[index] = i;