On Sun, Jan 12, 2014 at 5:27 AM, David Carlisle
<davidc(_at_)nag(_dot_)co(_dot_)uk> wrote:
I think the way to think of it is to see that given a sequence of nodes
$seq then count($seq) doesn't require you to access anything that you
haven't already accessed (even if you are in a streaming context and
some of the nodes are still being streamed)
If the context node has N children nodes, it isn't possible to know
that there are K children, unless at least these K children nodes (and
their sub-trees) are already read (confirmed to exist).
So, to test the existence of
node()[$K]
one will need to confirm this by reading through at least K children nodes.
Even worse, to test the existence of:
mySpecificNamedChild[1]
one may need to read *all* the children of the context node.
These observations show, that in general "count()" , using the chosen
terminology, is clearly an "absorption" operation and not an
"inspection" operation, though there is one exception when count() is
applied on nodes, whose number is statically known -- such as:
count(/)
count(..)
count(.)
Of course, it is meaningless to use the above three expressions,
because we already know what they would exactly produce ...
--
Cheers,
Dimitre Novatchev
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Truly great madness cannot be achieved without significant intelligence.
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To invent, you need a good imagination and a pile of junk
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Never fight an inanimate object
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To avoid situations in which you might make mistakes may be the
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Quality means doing it right when no one is looking.
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You've achieved success in your field when you don't know whether what
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