Precedence

[Bojan Knezovic]

Can someone shed some light here please, I'm desperate

x=-1;
int y=x++ + ++x;
System.out.println(y);

y is 0!
I thought it would be y=-1 + 0 but it seems to be y=-1 + 1.
How come??

[Michael Morris]

It is evaluated left to right:
1. y = x++ (At this point y = -1 and x now equals 0)
2. y = y + ++x (Now y = 0 and x = 1)

[Adrian Pang]

Just a guess, I think here's what happened:
x=-1
y=x++ + ++ x; // x= -1
x++ has the most precedence, so it becomes:
y= (-1) + ++x; // x = 0
++x is next:
y = (-1) + (1);
therefore the result is 0.
It is interesting to compare this with:
x = -1;
x += x++;
Which will give -2, in my mind the += operator works like:
int tmp = x;
x = tmp + x++;
Hope this helps and the above is correct...
Adrian

[Bojan Knezovic]

Originally posted by Michael Morris:
It is evaluated left to right:
1. y = x++ (At this point y = -1 and x now equals 0)
2. y = y + ++x (Now y = 0 and x = 1)

I thought x gets inceremented only AFTER the = operator (for #1, x++), isn't that what's pre and postfix notation all about... Oh well... :roll:
I thank you and Adrian.