[om] OM Floats (XML Representation)

[Richard Fateman]

I haven't looked (recently) at the Java treatment of IEEE NaN,
but unless it redefines the underlying hardware, there should be lots
of NaNs in it.  There may be one canonical NaN value (in each format)
if you do  x = NaN, but that doesn't prevent a program from using
a different NaN.

Before you take too much guidance from Java, you might also look at

http://www.cs.berkeley.edu/~wkahan/JAVAhurt.pdf

which contains a paper, "How Java's floating point hurts everyone 
everywhere".

It is my own view that the goals of clean algebraic specification and 
practical floating point
computation are probably irreconcilable, my own efforts included.  Over 
the years
I have written a number of papers relating IEEE floats and computer 
algebra, all of which
have been rejected by ISSAC program committee members as being irrelevant to
computer algebra. Maybe they are right, that they are mutually 
exclusive.  In which
case maybe OM should just encapsulate IEEE floats as some kind of 
foreign object.

(In case you wonder about what those papers might be about,
one can use signed infinities nicely in  interval arithmetic, and for 
retrospective
diagnostics. I think they are all on line.

I don't know if there is an OM CD for intervals yet.)

RJF


...............


Mike Dewar wrote:

>I agree with James - we ought to stick with the IEEE definition of NaN
>since the XSD one is so far out of step with other standards.  However
>Bill was right to note that Java only has one NaN value, even though the
>IEEE standard allows lots (as pointed out by Richard Fateman), so not
>everybody else is fully IEEE compliant either.  This should perhaps be
>pointed out in the standard as a possible issue for phrasebook
>developers.
>
>.....
>  
>

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