postincrement behaviour (differences between dmd and gdc)

[Derek Parnell]

On Wed, 24 Jan 2007 21:31:44 +0100, Nicolai Waniek wrote:

> Hello again,
> 
> I have a huge arguing going on with a friend of mine, which behaviour of
> x++ is the right one. This has in fact to do with D, so read on :)
> 
> This is our example application:
> 
> int x = 5;
> x = x++;
> x = x++;
> print(x);
> 
> 
> I argue: the result printed is 7.
> He argues: the result printed is 5.
> 
> the "++" operator is defined as: "returns the value and then increments
> it by 1". so I guess, the execution should be as follows:

I think that DMD is correct. The result should be 5. 

Based on the definition above, I think that the example is equivalent to
...

  int x = 5;
  int temp;

  // x = x++;
  temp = x;  // temp is now 5
  x = x + 1; // x is now 6
  x = temp;  // x is now 5

  // x = x++;
  temp = x;  // temp is now 5
  x = x + 1; // x is now 6
  x = temp;  // x is now 5

The key phrase is "returns the value and then increments" which I take it
to mean that it returns the value of the variable that it had prior to it
being incremented.

-- 
Derek Parnell