Re: [xsl] What does this XPath expression mean ?

["Kevin Grover" <kevin@xxxxxxxxxxxxxxx>]

On Sat, Mar 22, 2008 at 5:43 AM, Kamal <kbhatt@xxxxxxxxx> wrote:
>
>  I was in the middle of answering this, and I didn't want my good work to
>  go to waste, so I thought I would answer again.
>
>  Just looking at this:
>
>  [not(@label = preceding::*/@label)]
>
>
>  It is comparing the current label is exactly the same as the preceding
>  labels. For example,
>
>  <blah label="A">1</blah>
>  <blah label="A">2</blah>
>  <blah label="B">3</blah>
>  <blah label="B">4</blah>
>  <blah label="C">5</blah>
>
>  This will match on 2, 4, 5. As you can gather, that XPath is pretty much
>  useless without your dataset being sorted. This is an inefficient way of
>  grouping values. Your other post about the generate-id is a more
>  efficient way of doing this. Personally speaking, if you are not worried
>  too much about efficiency, I recommend sticking with this method. It is
>  easier to understand and doesn't rely on keys.
>

Actually, it picks up 1, 3, and 5 and does not matter if the list is
sorted (unless you change the relative order of elements with the same
label).  Why?  When 1 is selected there are no other nodes (preceding
nodes) with label="A", when 2 is _looked_ at, there is another node
(preceding node) with label="A" (namely 1), so it's excluded.