Re: [xsl] not()'ing a false variable, xalan 2.4.D1

Subject: Re: [xsl] not()'ing a false variable, xalan 2.4.D1
From: David N Bertoni/Cambridge/IBM <david_n_bertoni@xxxxxxxxxx>
Date: Thu, 7 Nov 2002 17:51:02 -0800



Hi Elizabeth,

> The reason I am trying to do this is because I have created a template
> that tests for a certain condition and returns true or false, for
> example:
>
>   <xsl:template name="boolean-function-template">
>     <xsl:param name="node-set"/>
>     <xsl:choose>
>       <xsl:when test="$node-set/x">
>         <xsl:value-of select="false()"/>
>       </xsl:when>
>       <xsl:when test="$node-set/y">
>         <xsl:value-of select="true()"/>
>       </xsl:when>
>       <xsl:otherwise>
>         <xsl:value-of select="false()"/>
>       </xsl:otherwise>
>      </xsl:choose>
>    </xsl:template>
>
>   <xsl:template match="/">
>
>     <xsl:variable name="variable">
>       <xsl:call-template name="boolean-function-template">
>         <xsl:with-param name="node-set" select="."/>
>       </xsl:call-template>
>     </xsl:variable>
>
>     <xsl:if test="not($variable)">

Since you only want a true value when there's a "y" element, this should
work:

   <xsl:variable name="variable" select="boolean($node-set/y)"/>

Even then, you don't really need a boolean variable, since a non-empty
node-set will evaluate to true and an empty one will evaluate to false.  So
the following expressions are equivalent:

   "boolean($node-set/y) = true()"

   "$node-set/y = true()"

Or is this a simplification of what you're trying to do, and the selection
criteria are more complex?  If so, you could create the variable as an RTF,
but you'd need to compare against the actual text "true" or "false", and
the not() function wouldn't work directly with the variable.  You'd need to
do something like "not($rtf = 'true')" or "not($rtf = 'false')".  I
wouldn't recommend that, but you could do it.

By the way, remember that xsl:value-of _always_ create a text node, so
you're never creating a boolean variable when you use it.

Dave


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