[Issue 8530] Float types default initializers doesn't work in class

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=8530



--- Comment #4 from Daniel Kozak <kozzi11 at gmail.com> 2012-08-15 07:29:25 PDT ---
(In reply to comment #3)
> (In reply to comment #2)
> > (In reply to comment #1)
> > > If you want to check for NaN, then use std.math.isNaN. As I understand it,
> > > there is no guarantee that two NaN values have the same bit pattern (at
> > > minimum, you have signed and unsigned NaN, and there may be more variations - I
> > > don't remember). isNaN returns true in both cases. So, I don't believe that
> > > this is a bug.
> > 
> > Thanks for your reply. However I still think it is a bug, because when I assign
> > TYPE.init to variable VAR of type TYPE, and then I compare VAR is TYPE.init, I
> > assumed it returns true;
> 
> Your assumption is not correct. If type.init is a signalling NaN, the bit
> pattern changes when you access it. It has nothing to do with classes.
> 
> More generally,
> 
> x = y;
> assert (x is y);
> 
> Fails if x is floating point and y is a signalling NaN.
> When reading from x, the 'quiet' bit of will be set, so that it reads a quiet
> NaN, not a signalling one.
> That's the way the hardware works, the same behaviour applies in any language
> that uses the hardware.

OK, but still I dont understand why others compilers(LDC,GDC) works as I expect
and why real type in DMD behave different.

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