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[Bug 7999] New: [XPath 2.0] Leading lone slash, and (/+5), (/-5)

From: <bugzilla@wiggum.w3.org>
Date: Wed, 21 Oct 2009 17:02:02 +0000
To: public-qt-comments@w3.org
Message-ID: <bug-7999-523@http.www.w3.org/Bugs/Public/>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=7999

           Summary: [XPath 2.0] Leading lone slash, and (/+5), (/-5)
           Product: XPath / XQuery / XSLT
           Version: Recommendation
          Platform: PC
        OS/Version: Windows NT
            Status: NEW
          Severity: normal
          Priority: P2
         Component: XPath
        AssignedTo: jonathan.robie@redhat.com
        ReportedBy: mike@saxonica.com
         QAContact: public-qt-comments@w3.org


In implementing erratum XQ.E34, concerning disambiguation of leading lone
slash, I have belatedly realized that the agreed wording has an unfortunate
effect on the expressions

/ + 5

/ - 5

These expressions were unambiguous and had a clear meaning in XPath 1.0. The
"+" or "-" is taken as a binary infix operator. The expressions weren't
particularly useful, except in the case of a document containing a single text
node: but such documents aren't that unusual in XSLT 1.0 stylesheets.

The effect of the erratum is to change the way these expressions are parsed, so
that the "+" or "-" is taken as a unary operator; the value of the expression
is now +5 or -5, irrespective of the content of the context document.

Although these expressions are likely to be rare, it seems irresponsible to
change the meaning of existing user code, especially when the old meaning is
more intuitive than the new.

I would therefore propose changing the agreed erratum text. Instead of "if the
token immediately following a slash can form the start of a RelativePathExpr,
then the slash must be the beginning of a PathExpr, not the entirety of it.",
we should say "if the token immediately following a slash can form the start of
a RelativePathExpr, and is not the token "+" or "-", then the slash must be the
beginning of a PathExpr, not the entirety of it."


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Received on Wednesday, 21 October 2009 17:02:07 UTC

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