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

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> 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?


I think that two expressions are "equivalent" if their evaluation
produces the same result on any XML document.

These *would be* equivalent, especially if "//" is removed from the
second expression.

As we know well, these are generally different:

   Websites

and

   //Websites


Cheers,

Dimitre

On Thu, Nov 1, 2012 at 6:01 AM, Costello, Roger L. <costello@xxxxxxxxx> 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
>



-- 
Cheers,
Dimitre Novatchev
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