Re: Feedback on grouping solution

> 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.honnen@xxxxxx <
xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:

> On 26.10.2019 19:03, Rick Quatro rick@xxxxxxxxxxxxxx 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 :)
> 
>


-- 
Cheers,
Dimitre Novatchev
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