Re: [xsl] Techniques for Sorting and Reducing Maps in XSLT 3/XPath 3?

["Eliot Kimber ekimber@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

Here is my current solution, which is definitely an improvement over my
earlier solution. I hadnbt realized (or it didnbt occur to me) that I
could use for-each-group on maps. Using for-each-group and grouping by a
specific field is certainly easy and straightforward:



For this data, the paths provide the course details, in particular, course ID
and locale. I also have to eliminate config.xml files that are not the ones
Ibm looking for, which I do just by counting the number of tokens in the
path.



    <xsl:variable name="candidate-configs" as="map(*)*"
      select="collection($courses-dir ||
'?recurse=yes;metadata=yes;match=config.xml')"
    />

    <!-- Select configurations that are in the appropriate locale and that
         are course configurations and not course content configurations
(config.xml
         is used both for course description and within the course content
directory).

         Result is a sequence of maps, one for each selected candidate
course.
      -->
    <xsl:variable name="configs-to-use" as="map(*)*">
      <xsl:for-each select="$candidate-configs">
        <xsl:variable name="cand" as="map(*)" select="."/>
        <xsl:variable name="path-base" as="xs:string" select="$cand?name"/>
        <xsl:variable name="path" as="xs:string"
select="substring-after($path-base, $courses-dir || '/')"/>
        <xsl:variable name="tokens" as="xs:string*" select="tokenize($path,
'/')"/>
        <xsl:variable name="course-group" as="xs:string"
select="$tokens[1]"/>
        <xsl:variable name="course-id" as="xs:string" select="$tokens[2]"/>
        <xsl:variable name="locale" as="xs:string" select="$tokens[3]"/>
        <xsl:variable name="version" as="xs:string" select="$tokens[4]"/>
        <xsl:variable name="new-map" as="map(*)"
          select="
          map{
          'course-group' : $course-group,
          'course-id' : $course-id,
          'locale' : $locale,
          'version' : $version,
          'course-key' : ($course-group, $course-id) => string-join('^'),
          'course-key-locale' : ($course-group, $course-id, $locale) =>
string-join('^')
          }"
        />
        <xsl:if test="(empty($locales) or (exists($locales) and $locale =
$locales)) and count($tokens) eq 6">
          <xsl:sequence select="map:merge((., $new-map))"/>
        </xsl:if>
      </xsl:for-each>
    </xsl:variable>

    <!-- Now group by course ID and locale in order to select the highest
version of each course. -->
    <xsl:variable name="course-configs-by-course-key-locale"
as="map(xs:string, map(*))">
      <xsl:map>
        <xsl:for-each-group select="$configs-to-use"
group-by=".?course-key-locale">
          <xsl:variable name="courses-for-locale" as="map(*)*"
select="current-group()"/>
          <xsl:variable name="highest-version" as="xs:string"
            select="$courses-for-locale ! map:get(., 'version') ! xs:double(.)
=> max() => format-number('#.0')"
          />
          <xsl:variable name="course-map" as="map(*)*"
            select="
              $courses-for-locale !
              (if (map:get(., 'version') eq $highest-version)
               then .
               else ()
              )"

          />
          <xsl:sequence select="map:entry(current-grouping-key(),
$course-map)"/>
        </xsl:for-each-group>
      </xsl:map>
    </xsl:variable>



Cheers,



E.

--

Eliot Kimber

http://contrext.com







From: "Mukul Gandhi gandhi.mukul@xxxxxxxxx"
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
Reply-To: <xsl-list@xxxxxxxxxxxxxxxxxxxxxx>
Date: Saturday, July 7, 2018 at 2:01 AM
To: <xsl-list@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [xsl] Techniques for Sorting and Reducing Maps in XSLT 3/XPath
3?



On Fri, Jul 6, 2018 at 9:58 PM, Liam R. E. Quin liam@xxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:

On your xsl:iterate question, i'd generally try for-each and/or for-
each-group before xsl:iterate. The reason is largely that i think it
encourage thinking in terms of a functional mapping rather than an
imperative loop, and that can help clarity of thought.



 I'm still not up to speed with using XSLT 3.0 (but I'm trying to). But I
agree with your point Liam.







--

Regards,

Mukul Gandhi

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