Re: [xsl] Outputing a node whose value appears only once

["G. Ken Holman" <gkholman@xxxxxxxxxxxxxxxxxxxx>]

At 2005-07-18 21:00 -0700, Mukul Gandhi wrote:
> I am trying to eliminate duplicates with the following
> logic..
> ...
>    <xsl:for-each select="(a/* | c/*)[not((. =
> preceding-sibling::a) | (. = preceding-sibling::c) |
> (. = following-sibling::a) | (. =
> following-sibling::a))]">
> ...
> Saxon 8.4 is giving error -
> Error on line 7 of
> file:/C:/xml/xsleg/xslt/example1.xsl:
>   XPTY0004: Required item type of first operand of '|'
> is node(); supplied value
>  has item
>   type xs:boolean
>
> Whereas Xalan-J 2.6.0 gives following error -
> Error at xsl:for-each on line 7 of
> file:///C:/xml/xsleg/xslt/example1.xsl:
>   The value is not a node-set
>
> Can anyone tell where is the problem?

The error messages are unambiguous and say it all ... you are trying to use 
the union operator with an operand that is not a node set.

> And how I can solve it?

You are using "|" as "or" and that isn't part of the XPath syntax for 
boolean operators ... "|" is *only* for the union of node sets.

If I've guessed your intent correctly you probably want:

  <xsl:for-each select="(a/* | c/*)[not((. = preceding-sibling::a) or (. = 
preceding-sibling::c) or (. = following-sibling::a) or (. = 
following-sibling::a))]">

This is a *very* common misconception by my XSLT students who are trying to 
use "or" in my in-class exercises and type "|" because of their programming 
background.

I hope this helps.

. . . . . . Ken

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