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[Bug 4881] Should -NaN be allowed and given a meaning?

From: <bugzilla@wiggum.w3.org>
Date: Wed, 25 Jul 2007 13:32:40 +0000
To: www-xml-schema-comments@w3.org
Message-Id: <E1IDgym-0007iV-H5@wiggum.w3.org>


           Summary: Should -NaN be allowed and given a meaning?
           Product: XML Schema
           Version: 1.1 only
          Platform: Macintosh
        OS/Version: All
            Status: NEW
          Keywords: unclassified
          Severity: normal
          Priority: P2
         Component: Datatypes: XSD Part 2
        AssignedTo: cmsmcq@w3.org
        ReportedBy: cmsmcq@w3.org
         QAContact: www-xml-schema-comments@w3.org

In his survey of the impact of precision decimal on XPath and XQuery
[member-only link], Don Chamberlin observes

    In 754r Section 5.10 we read "totalorder(-NaN, number) is 
    true where -NaN represents a NaN with negative sign bit". 
    (But there is no negative NaN value in XML Schema.)

It would appear from this that IEEE 754R assigns distinct meaning,
for ordering purposes, to the sign bit of NaN values.  Our
description of precisionDecimal requires the sign to be absent
when the numericalValue is notANumber.  Our float and double
types have a NaN, but no negative NaN.

If IEEE 754 does assign ordering or processing semantics to 
-NaN, it may perhaps be useful for XPath and the other QT
specs if XSDL distinguishes NaN and -NaN.

Should our description of NaN be modified to follow 754?
Received on Wednesday, 25 July 2007 13:32:45 UTC

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