Re: [xsl] Are these equivalent XPath expressions for determining that there are no duplicates in a list of items?

[David Carlisle <davidc@xxxxxxxxx>]

On 01/11/2012 13:01, Costello, Roger L. wrote:
> Hi Folks,
>
> Are there no duplicate websites in this list:
>
> <Websites> <Website id="Amazon"> http://www.amazon.com </Website>
> <Website id="Apple"> http://www.apple.com </Website> <Website
> id="Ebay"> http://www.ebay.com </Website> <Website id="Google">
> http://www.google.com </Website> <Website id="Microsoft">
> http://www.microsoft.com </Website> <Website id="VirginAtlantic">
> http://www.virgin-atlantic.com </Website> </Websites>
>
> Here is an XPath 2.0 expression to answer that question (thanks to
> Dimitre):
>
> empty(Websites/*[index-of(../*,.)[2]])
>
> Here is an XPath 1.0 expression to answer that question:
>
> not(//Websites/*[. = preceding-sibling::*])
>
> Are there any situations where those two XPath expressions differ in
> their answer?
>
> /Roger

both would be rather inefficient in XSLT where you could use keys or
for-each-group. They are different mainly because the second one uses
//at the front (which isn't related to the duplicate removal. You should
use // on either both or neither of them depending what you want).  The 
other difference is that index-of uses eq equality whereas you have used 
= not eq in the second form That probably only makes a difference in 
this context if there is some weird schema typing involved.

David