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RE: Addition/Subtraction of numbers.
- From: Wendell Piez <wapiez at mulberrytech dot com>
- To: xsl-list at lists dot mulberrytech dot com
- Date: Wed, 23 Jan 2002 18:52:45 -0500
- Subject: RE: [xsl] Addition/Subtraction of numbers.
- Reply-to: xsl-list at lists dot mulberrytech dot com
Joshua,
At 06:24 PM 1/23/02, you wrote:
>I have the understanding that the XPath number() function will return the
>string 'NaN' if the parameter passed in is not a number.
No, not exactly, it will return the number Not-a-Number (which if
stringified comes out 'NaN').
> Though, at a lower level, won't the same function called twice with
> identical parameter(s) return the same thing?
Yes, it will (thank goodness).
> So, when would your test of "number($t1) = number($t1)" fail?
When either number is Not-a-number. According to the Java Language
Specification, which is cited by XPath (section 3.5) for its summary of the
behavior of IEEE 754 double-precision numbers, "The equality operator ==
returns false if either operand is NaN" (of course in XPath the operator is
'=' ... for now).
So NaN is not equal to itself.
It's confusing, but it comes with the territory of a number that is
Not-a-Number. :-> Trust Jeni to be able to use this wrinkle productively.
Cheers,
Wendell
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Wendell Piez mailto:wapiez@mulberrytech.com
Mulberry Technologies, Inc. http://www.mulberrytech.com
17 West Jefferson Street Direct Phone: 301/315-9635
Suite 207 Phone: 301/315-9631
Rockville, MD 20850 Fax: 301/315-8285
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