Re: [xsl] Excluding an element with specific content from an <xsl:sort> call

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

At 2010-01-31 03:07 +0100, Hermann Stamm-Wilbrandt wrote:
> Under the assumption that 'A' only appears as length-1 string in Prefix
> the following diff makes that stylesheet work on XSLT 1.0 processors:
>
> $ diff mark.xsl mark1.xsl
> 10c10
> <        <xsl:sort select="if( Prefix!='A' ) then Prefix else ''"/>
> ---
> >        <xsl:sort select="translate(Prefix,'A','')"/>
> $

When I find I have to do conditional expressions in XPath 1 I try to 
find a way of expressing the logic in a predicate, which in this case 
would not restrict the solution to only singleton-character strings:

   <xsl:sort select="Prefix[.!='A']"/>

... as illustrated below.

Note this can even work in Path 1 when you need to express a choice 
of some kind between nodes.  What if the original requirement were to 
use the Prefix1 child in one condition and the Prefix2 child in 
another condition?  In XPath 2 this would be simply:

   <xsl:sort select="if( $condition ) then Prefix1 else Prefix2"/>

... but without a conditional in XPath 1, I would approach this something like:

   <xsl:sort select="Prefix1[$condition] | Prefix2[not($condition)]"/>

Soon after the release of XSLT/XPath in 1999 it was necessary to come 
up with such schemes for conditional XPath expressions to meet 
real-world requirements from my customers.  Modify the original 
poster's requirement that Prefix2 is optional but has precedence over 
Prefix1 when both are present, knowing that Prefix2 is after Prefix1 
in document order:

     <xsl:sort select="(Prefix1 | Prefix2)[last()]"/>

... or more generally regardless of document order:

     <xsl:sort select="Prefix1[not(../Prefix2)] | Prefix2"/>

Just remember when dealing with nodes in XPath 1 to express the union 
of the two mutually-exclusive node sets expressing the binary results 
of the condition.  Only one of the union operands will be non-empty.

I hope this is considered helpful.

. . . . . . . . . . . Ken

t:\ftemp>type mark.xml
<tests>
 <record>
  <order>1</order>
  <Prefix>D</Prefix>
 </record>
 <record>
  <order>2</order>
  <Prefix>A</Prefix>
 </record>
 <record>
  <order>3</order>
  <Prefix>L</Prefix>
 </record>
 <record>
  <order>4</order>
  <Prefix>A</Prefix>
 </record>
 <record>
  <order>5</order>
 </record>
 <record>
  <order>6</order>
  <Prefix>A</Prefix>
 </record>
 <record>
  <order>7</order>
 </record>
 <record>
  <order>8</order>
  <Prefix>L</Prefix>
 </record>
 <record>
  <order>9</order>
  <Prefix>D</Prefix>
 </record>
</tests>

t:\ftemp>call xslt mark.xml mark.xsl
<?xml version="1.0" encoding="utf-8"?><tests><record>
  <order>2</order>
  <Prefix>A</Prefix>
 </record><record>
  <order>4</order>
  <Prefix>A</Prefix>
 </record><record>
  <order>5</order>
 </record><record>
  <order>6</order>
  <Prefix>A</Prefix>
 </record><record>
  <order>7</order>
 </record><record>
  <order>1</order>
  <Prefix>D</Prefix>
 </record><record>
  <order>9</order>
  <Prefix>D</Prefix>
 </record><record>
  <order>3</order>
  <Prefix>L</Prefix>
 </record><record>
  <order>8</order>
  <Prefix>L</Prefix>
 </record></tests>
t:\ftemp>type mark.xsl
<?xml version="1.0" encoding="US-ASCII"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
                version="1.0">

<xsl:template match="tests">
  <xsl:copy>
    <xsl:for-each select="record">
      <xsl:sort select="Prefix[.!='A']"/>
      <xsl:copy-of select="."/>
    </xsl:for-each>
  </xsl:copy>
</xsl:template>

</xsl:stylesheet>

t:\ftemp>rem Done!



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