xsl-list
[Top] [All Lists]

Re: [xsl] Feedback on grouping solution

2019-10-26 20:24:22
Actually, we don't need 2-pass processing!

Below is a really short and simple *XSLT 1* transformation -- it is just 26
lines -- *40% shorter* than the XSLT 3.0 transformation provided by Martin.

Enjoy:

<xsl:stylesheet version="1.0" xmlns:xsl="
http://www.w3.org/1999/XSL/Transform";>
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

  <xsl:template match="node()|@*" name="identity">
    <xsl:copy>
      <xsl:apply-templates select="node()|@*"/>
    </xsl:copy>
  </xsl:template>

  <xsl:template match="step"><xsl:apply-templates
select="*[1]"/></xsl:template>

  <xsl:template match="step/*">
    <xsl:param name="pAdjustments" select="0"/>
    <xsl:variable name="vNeedsAdjustment" select="self::figure and
(count(preceding-sibling::*) +1 + $pAdjustments) mod 2 = 1"/>

    <xsl:if test="$vNeedsAdjustment">
      <spacer/>
    </xsl:if>
    <xsl:call-template name="identity"/>

    <xsl:apply-templates select="following-sibling::*[1]">
      <xsl:with-param name="pAdjustments" select="$pAdjustments +
$vNeedsAdjustment"/>
    </xsl:apply-templates>
  </xsl:template>
</xsl:stylesheet>

Cheers,
Dimitre


On Sat, Oct 26, 2019 at 4:22 PM Dimitre Novatchev 
dnovatchev(_at_)gmail(_dot_)com <
xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:

Now waiting for Dimitre posting a less "fancy"
but equally compact XSLT 1 solution :)

The following is a 48-lines XSLT 2.0 solution (2 passes -- equivalent XSLT
1.0 solution is easy to produce but will need the vendor:node-set()
extension function).

Martin's XSLT 3.0 solution is 43 lines when <xsl:stylesheet> and
<xsl:output> are added. So the difference in number of lines is not big --
12% and I believe the XSLT 2 solution below is less complex and more easily
understandable.

Maybe I am biased, but I personally believe that it is better to use the
standard XPath 3 functions fold-left() and fold-right() in the spirit of
functional programming. <xsl:iterate> instead helps people avoid thinking
using the concepts of functional programming. Also, its definition is so
complex that I personally needed more than an hour to find out / construct
what cases of its usage are possible and which are mutually exclusive.

Here is the transformation:

<xsl:stylesheet version="2.0" xmlns:xsl="
http://www.w3.org/1999/XSL/Transform";>
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

  <xsl:variable name="vPass1Result"><xsl:apply-templates
select="/*"/></xsl:variable>

  <xsl:template match="node()|@*" mode="#default pass2">
    <xsl:copy>
      <xsl:apply-templates select="node()|(@* except @stepChild)"
mode="#current"/>
    </xsl:copy>
  </xsl:template>

  <xsl:template match="/">
    <xsl:apply-templates select="$vPass1Result/*" mode="pass2"/>
  </xsl:template>

  <xsl:template match="step"><xsl:apply-templates/></xsl:template>

  <xsl:template match="step/*">
    <xsl:copy>
      <xsl:apply-templates select="@*"/>
      <xsl:attribute name="stepChild">
        <xsl:number level="any" count="/*/step/*"/>
      </xsl:attribute>
      <xsl:apply-templates select="node()"/>
    </xsl:copy>
  </xsl:template>

  <xsl:template match="/*" mode="pass2">
   <xsl:copy>
     <xsl:apply-templates select="*[1]" mode="pass2"/>
   </xsl:copy>
  </xsl:template>

  <xsl:template match="/*/*" mode="pass2">
    <xsl:param name="pAdjustments" select="0"/>
    <xsl:variable name="vNeedsAdjustment" select="self::figure and
(count(preceding-sibling::*[@stepChild]) +1 + $pAdjustments) mod 2 = 1"/>

    <xsl:if test="$vNeedsAdjustment">
      <spacer/>
    </xsl:if>
    <xsl:next-match/>

    <xsl:apply-templates select="following-sibling::*[1]" mode="pass2">
      <xsl:with-param name="pAdjustments" select="$pAdjustments +
(if($vNeedsAdjustment) then 1 else 0)"/>
    </xsl:apply-templates>
  </xsl:template>
</xsl:stylesheet>


Cheers,
Dimitre



On Sat, Oct 26, 2019 at 12:06 PM Martin Honnen 
martin(_dot_)honnen(_at_)gmx(_dot_)de <
xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:

On 26.10.2019 19:03, Rick Quatro rick(_at_)rickquatro(_dot_)com wrote:

I need to process the <step> child elements so that the <figure>
elements are always on the "right" (even-numbered position) in the
output. Immediate children of the <procedure> do not factor into the
odd/even sequence.

The first child of each group of adjacent <step> elements starts a new
odd/even series. To ensure that the each <figure> is in an even-numbered
position, I want to insert a <spacer> element where it is required.

Here is my stylesheet. My basic question is: is there a better or more
efficient way to do this?

I think with XSLT 3 it is possible to use xsl:iterate on the child
elements of the adjacent steps found by grouping:

     <xsl:mode on-no-match="shallow-copy"/>

     <xsl:template match="procedure">
         <xsl:copy>
             <xsl:for-each-group select="*"
group-adjacent="boolean(self::step)">
                 <xsl:choose>
                     <xsl:when test="current-grouping-key()">
                         <xsl:iterate select="current-group()/*">
                             <xsl:param name="position-in-output"
select="1"/>
                             <xsl:apply-templates select=".">
                                 <xsl:with-param
name="position-in-output" select="$position-in-output"/>
                             </xsl:apply-templates>
                             <xsl:next-iteration>
                                 <xsl:with-param name="position-in-output"
                                     select="if (self::figure and
$position-in-output mod 2 = 1)
                                             then $position-in-output + 2
                                             else $position-in-output +
1"/>
                             </xsl:next-iteration>
                         </xsl:iterate>
                     </xsl:when>
                     <xsl:otherwise>
                         <xsl:apply-templates select="current-group()"/>
                     </xsl:otherwise>
                 </xsl:choose>
             </xsl:for-each-group>
         </xsl:copy>
     </xsl:template>

     <xsl:template match="step/figure">
         <xsl:param name="position-in-output"/>
         <xsl:if test="$position-in-output mod 2 = 1">
             <spacer/>
         </xsl:if>
         <xsl:next-match/>
     </xsl:template>



Now waiting for Dimitre posting a less "fancy" but equally compact XSLT
1 solution :)




--~----------------------------------------------------------------
XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
EasyUnsubscribe: http://lists.mulberrytech.com/unsub/xsl-list/1167547
or by email: xsl-list-unsub(_at_)lists(_dot_)mulberrytech(_dot_)com
--~--
<Prev in Thread] Current Thread [Next in Thread>