[Bug 5876] New: [XPath] Is it an error for an operator to be contained in parentheses?

http://www.w3.org/Bugs/Public/show_bug.cgi?id=5876

           Summary: [XPath] Is it an error for an operator to be contained
                    in parentheses?
           Product: XPath / XQuery / XSLT
           Version: Recommendation
          Platform: All
               URL: http://www.w3.org/TR/xpath20/#id-precedence-order
        OS/Version: All
            Status: NEW
          Severity: trivial
          Priority: P2
         Component: XPath
        AssignedTo: chamberl@almaden.ibm.com
        ReportedBy: zongaro@ca.ibm.com
         QAContact: public-qt-comments@w3.org


A co-worker pointed out that section A.4 of XPath 2.0[1] (and equally, of
XQuery 1.0) states that "operators are summarized here to make clear the order
of their precedence from lowest to highest. Operators that have a lower
precedence number cannot be contained by operators with a higher precedence
number."  The table that follows that statement has entries for the various
operators, including binary plus and minus, with a precedence of eight, and
parentheses, square brackets and brace brackets, with a precedence of nineteen.

Because parentheses have a higher precedence number than binary plus, the only
conclusion seems to be that a plus operator cannot be contained in parentheses.
 Clearly that's false, and some special treatment is needed.

Perhaps the third sentence of the first paragraph could be reworded to say
"Operators that have a lower precedence number cannot be contained by operators
with a higher precedence number, except that any operator can be contained in
parentheses, brace brackets and square brackets, and an operator can contain an
expression in parentheses, brace brackets or square brackets that contains
another operator with lower precedence number than the operator," where the two
occurrences of ", brace brackets" only apply to XQuery.

(Of course these statements about operators containing operators really should
be speaking of expressions containing operators or expressions whose operands
contain particular operators, but I didn't want to go too far with the proposed
rewording.)

Note also that braces appear in the table for XPath, but exist only in XQuery.

[1] http://www.w3.org/TR/xpath20/#id-precedence-order


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Received on Friday, 18 July 2008 14:47:02 UTC