[xsd-users] comparison operation

[Rizzuto, Raymond]

Boris,

Is there a way to use the new 3.2.0 feature that address the precision of float/double to "fix" the representation issue?

I.e. if my original double is rounded to XSD_CXX_TREE_DOUBLE_PRECISION places.  If I take the rounded value, serialize and deserialize it via my XSD-generated library, would the deserialized value be guaranteed to compare equal to the rounded version I serialized?

Ray

-----Original Message-----
From: Boris Kolpackov [mailto:boris at codesynthesis.com]
Sent: Monday, July 14, 2008 4:19 PM
To: Rizzuto, Raymond
Cc: xsd-users at codesynthesis.com
Subject: Re: [xsd-users] comparison operation

Hi Ray,

Rizzuto, Raymond <Raymond.Rizzuto at sig.com> writes:

> So, there are two effects going on here. One is that the serialization to
> XML loses digits after microseconds. The other is conversion from a string
> to a double can run into representation issues.

Correct on both counts.


> I am not sure if it is worth addressing the first issue - microseconds
> may be sufficient for most purposes. In my code, I think I can limit
> the value to 6 decimal places fairly easily.

Yes, we have to pick some default value and microseconds seems like
a reasonable compromise. You always have an option to customize the
dateTime type and serialize the seconds component with your desired
precision.


> The representation issue isn't an issue for precision, but it certainly
> affects any comparison of types that rely on doubles. I'm not sure if
> there is a good answer here.

I don't think there is a practical solution to this one since that's
how floating point types work. So the only suggestion I can offer is
to choose floating point values for your test so that they don't
trigger this problem.

Boris

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