On Friday, 28 March 2014 at 16:54:49 UTC, Benjamin Thaut wrote:
I had a bug which came down to the following line today:
m_takeIndex = m_takeIndex++;
Actually this line does nothing. m_takeIndex remains at exactly
the same value as before (tested with dmd 2.065).
Can someone please explain why?
IT does nothing because that's post-increment: EG "save the
current value, increment, return the old value".
Then you assign back the old value, effectively putting you back
where you started:
int i = 5;
i = i++; //i is 5
then
i = 5; //i was incremented to 6
then
i is 5 again;
And would be suitable to warn about this, if it is correct
behaviour?
The problem here though is that we are talking about a "logical"
no side effect: It *does* something, you just can't observe it.
Imagine this:
//----
void fun(ref i, ref j)
{
i = j++;
}
void main()
{
int a = 5;
fun(a, a); //do nothing?
}
//----
This is to contrast with "i + j;" which is an *actual* no op.
