Robert,
At 02:53 PM 9/4/2003, you wrote:
but that was my point. the sample XSL i showed for calculating the
minimum value was *treating* a node-set as if the individual elements
were numbers, and was comparing them numerically.
<xsl:value-of select="$nodes[not($nodes < .)]"/>
how would this be interpreted?
As in plenty of other cases in XSLT (1.0), the processor is performing a
bit of data type casting for you -- turning nodes into numbers. The rules
for this are detailed in the XPath spec. Here, when a node must be
construed as a number (required by the less-than operation), it is (a)
turned into a string by taking its string value, and (b) then turned into a
number following the string-to-number rules you'd expect.
(This particular routine is also relying on a rule of how to compare
numerical values with node-sets containing more than one node -- compare
each pairing in turn, return true if any are true.)
the book refers to this as calculating
"the minimum value of a node set", which to my mind is viewing the
"nodes" as numerical values.
Their *values* are numbers (as they are also strings, if we need strings).
Any string can be turned into a number ... if it can't, it is anyhow -- the
number not-a-number (NaN). And any node can be turned into a string. Ergo, etc.
But really the technique you're citing from the book is robust only in such
cases where you know ahead of time the nodes in the set will all cast to
numbers cleanly.
i wasn't trying to suggest that numbers
were actual nodes, only that they were being "treated" that way by
the above expression.
Yes, XPath 1.0 invites this kind of "treat as if" thinking. Most of the
time, it's a welcome feature of the language. Sometimes it gets us into
tangles.
All of this will change drastically in XPath 2.0, where casts must be made
explicitly. Then we get to see what life is like on the other side of the
fence.
Cheers,
Wendell
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Wendell Piez
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