Re: [xsl] Checking if a variable has a value

["Norm Tovey-Walsh ndw@xxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

"Jean-Paul Rehr rehrjb@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
writes:
> In Xquery the following returns false:
>
> let $x := ()
> return
>       if (exists($x)) then true() else false()
>
> Are you stating that the equivalent cannot happen in XSL variables?
> I'm asking this mostly because I've not had the need to explore this
> until now and am ignorant about it.

It can, if the value of the variable is the empty sequence. Consider
this stylesheet:

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
                xmlns:xs="http://www.w3.org/2001/XMLSchema";
                exclude-result-prefixes="xs"
                version="3.0">

<xsl:param name="x" select="()"/>

<xsl:template name="xsl:initial-template">
  <exists>
    <xsl:choose>
      <xsl:when test="exists($x)">true</xsl:when>
      <xsl:otherwise>false</xsl:otherwise>
    </xsl:choose>
  </exists>
</xsl:template>

</xsl:stylesheet>

It will output b<exists>false</exists>b by default, but will output
b<exists>true</exists>b if you specify a value for $x, even the empty
string.

                                        Be seeing you,
                                          norm

--
Norman Tovey-Walsh <ndw@xxxxxxxxxx>
https://nwalsh.com/

> Where it is permissible both to die and not to die, it is an abuse of
> valour to die.--Mencius

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