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

           Summary: Float types default initializers doesn't work in class
           Product: D
           Version: D2
          Platform: x86_64
        OS/Version: Linux
            Status: NEW
          Severity: major
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: kozzi11@gmail.com


--- Comment #0 from Daniel Kozak <kozzi11@gmail.com> 2012-08-10 02:27:21 PDT ---
Created an attachment (id=1136)
problematic code

When I create class with some float variable without value, then call some method on this class and test float variable for default value, it doesnt work.

My code is in in attachment

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On Friday, 10 August 2012 at 09:27:25 UTC, Daniel Kozak wrote:
> http://d.puremagic.com/issues/show_bug.cgi?id=8530
>
>            Summary: Float types default initializers doesn't work in class
>            Product: D
>            Version: D2
>           Platform: x86_64
>         OS/Version: Linux
>             Status: NEW
>           Severity: major
>           Priority: P2
>          Component: DMD
>         AssignedTo: nobody@puremagic.com
>         ReportedBy: kozzi11@gmail.com
>
>
> --- Comment #0 from Daniel Kozak <kozzi11@gmail.com> 2012-08-10 02:27:21 PDT ---
> Created an attachment (id=1136)
> problematic code
>
> When I create class with some float variable without value, then call some
> method on this class and test float variable for default value, it doesnt work.
>
> My code is in in attachment

Problematic code:
-----------------------------------------------------------
module main;

import std.stdio;

class A {
	private float floatInClass;
	
	public void tryfloatInitValue() {
		float floatInLocalScope;
		
		if (floatInClass is float.init) {
			writeln("floatInClass OK");
		} else {
			writeln("floatInClass ERR");
		}
		
		if (floatInLocalScope is float.init) {
			writeln("floatInLocalScope OK");
		} else {
			writeln("floatInLocalScope ERR");
		}
	}
}

void main(string[] args)
{
	A smth = new A();
	smth.tryfloatInitValue();
}

----------------------------------------------------------
Same for double, but for real type it is ok

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


Jonathan M Davis <jmdavisProg@gmx.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jmdavisProg@gmx.com


--- Comment #1 from Jonathan M Davis <jmdavisProg@gmx.com> 2012-08-10 03:00:35 PDT ---
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.

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



--- Comment #2 from Daniel Kozak <kozzi11@gmail.com> 2012-08-10 03:19:42 PDT ---
(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;

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On 8/10/2012 2:30 AM, Daniel Kozak wrote:
> Problematic code:

Replying to bug reports in the newsgroup generally means your reply will be overlooked. Please reply on bugzilla.

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


Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |clugdbug@yahoo.com.au


--- Comment #3 from Don <clugdbug@yahoo.com.au> 2012-08-15 06:23:41 PDT ---
(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.

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



--- Comment #4 from Daniel Kozak <kozzi11@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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http://d.puremagic.com/issues/show_bug.cgi?id=8530


Iain Buclaw <ibuclaw@ubuntu.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ibuclaw@ubuntu.com


--- Comment #5 from Iain Buclaw <ibuclaw@ubuntu.com> 2012-08-15 08:09:25 PDT ---
(In reply to comment #4)
> (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.


GDC calls memcmp() between the two floating values - dunno what DMD does...

Regards
Iain

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