RE: AW: [xsl] tricky problem filtering input and counting output

["Trevor Nicholls" <trevor@xxxxxxxxxxxxxxxxxx>]

Hi Wendell, (& thanks Patrick)

I think running a separate pass to filter the input XML file is the simplest
solution and I will try that straight away. I don't know why it didn't occur
to me already. Strangely (it seems to me) I typed up the whole post and before
wondering what to put in the subject. Now that I look at the subject, I see
that I practically described a two-step solution in half a sentence :-(

But seeing as you asked, here is what is going on with the filtering.

 <xsl:param name="filterversions" />
 <xsl:param name="filterplatforms" />

 <xsl:template name="filter-output">
  <xsl:param name="version" />
  <xsl:param name="platform" />
 <!-- version -->
  <xsl:variable name="versionchk">
   <xsl:choose>
    <xsl:when test="$version != ''">
     <xsl:if test="contains($filterversions,$version)">
      <xsl:text>Y</xsl:text>
     </xsl:if>
    </xsl:when>
    <xsl:otherwise>
     <xsl:text>Y</xsl:text>
    </xsl:otherwise>
   </xsl:choose>
  </xsl:variable>
 <!-- platform -->
  <xsl:variable name="platformchk">
   <xsl:choose>
    <xsl:when test="$platform != ''">
     <xsl:if test="contains($filterplatforms,$platform)">
      <xsl:text>Y</xsl:text>
     </xsl:if>
    </xsl:when>
    <xsl:otherwise>
     <xsl:text>Y</xsl:text>
    </xsl:otherwise>
   </xsl:choose>
  </xsl:variable>
 <!-- all together now -->
  <xsl:if test="concat($versionchk,$platformchk) = 'YY'">
   <xsl:text>Y</xsl:text>
  </xsl:if>
 </xsl:template>

My original sample had
 <xsl:call-template name="filter-output" />

but this template has some parameters of course, which are obtained either
from version/platform attributes on the context element (document or section)
or from higher up the node tree, or from an external document.

  <xsl:variable name="select">
   <xsl:call-template name="filter-output">
    <xsl:with-param name="version">
     <xsl:call-template name="get-version" />
    </xsl:with-param>
    <xsl:with-param name="platform" select="@platform" />
   </xsl:call-template>
  </xsl:variable>

where get-version is something like this:

 <xsl:template name="get-version">
  <xsl:variable name="localv">
   <xsl:value-of select="(ancestor-or-self::*/@version[. != ''])[last()]" />
  </xsl:variable>
  <xsl:variable name="external">
   <xsl:value-of select="document('catalog.xml',/)/files/file[. =
$me]/@version" />
  </xsl:variable>
  <xsl:choose>
   <xsl:when test="$localv != ''">
    <xsl:value-of select="$localv" />
   </xsl:when>
   <xsl:otherwise>
    <xsl:value-of select="$externalv" />
   </xsl:otherwise>
  </xsl:choose>
 </xsl:template>

$me is another global parameter identifying the XML file.

The expression for $localv is the way it is because I may need to use min() or
max() instead of last().


And now I expect you to glance at that and say, "yes, pipelining" without a
moment's thought :-)


Cheers
Trevor

-----Original Message-----
From: Wendell Piez [mailto:wapiez@xxxxxxxxxxxxxxxx]
Sent: Wednesday, 23 February 2011 6:25 a.m.
To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
Subject: Re: AW: [xsl] tricky problem filtering input and counting output

Hi,

On 2/22/2011 9:44 AM, Szabo, Patrick (LNG-VIE) wrote:
> I hope I'm imagining this correctly. Couldn't you filter the input
> before you do the counting ?!
>
> You could dump the document and sections elements you don't need and
> count afterwards.

Yes: Trevor's Gordian knot can be cut by pipelining. Filter the document
first, then run the transformation to generate the output.

A solution in one pass is also possible -- and might even be fairly
clean -- but how it would work best might depend on details of the
filtering requirement. Trevor, you haven't shown us the "filter-output"
template so we don't know what it does and whether it can be refactored
and simplified.

Also, much is possible in XSLT 2.0. For example, if that logic were in a
function instead of a template....

Cheers,
Wendell

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Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
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