Re: [xsl] Feedback on grouping solution

Subject: Re: [xsl] Feedback on grouping solution
From: "Dimitre Novatchev dnovatchev@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
Date: Sat, 26 Oct 2019 23:22:14 -0000
> 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

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="";>
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

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

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

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

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

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

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

  <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">

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


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 :)

Dimitre Novatchev
Truly great madness cannot be achieved without significant intelligence.
To invent, you need a good imagination and a pile of junk
Never fight an inanimate object
To avoid situations in which you might make mistakes may be the
biggest mistake of all
Quality means doing it right when no one is looking.
You've achieved success in your field when you don't know whether what
you're doing is work or play
To achieve the impossible dream, try going to sleep.
Facts do not cease to exist because they are ignored.
Typing monkeys will write all Shakespeare's works in 200yrs.Will they write
all patents, too? :)
Sanity is madness put to good use.
I finally figured out the only reason to be alive is to enjoy it.

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