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Re: [xsl] XSLT repetition constructs comparison

2021-01-14 04:28:47
Am 14.01.2021 um 10:05 schrieb Mukul Gandhi mukulg(_at_)softwarebytes(_dot_)org:
Hi all,
   I'm comparing the functionality of, XSLT repetition constructs xsl:for-each and xsl:iterate (versions 2.0 & 3.0). Below is my example use case, and the corresponding XSLT solutions from my side,

XML input document:

<?xml version="1.0"?>
<students>
    <student>
       <rollNo>1</rollNo>
       <fName>Sharon</fName>
       <lName>Adler</lName>
    </student>
    <student>
       <rollNo>2</rollNo>
       <fName>Anders</fName>
       <lName>Berglund</lName>
    </student>
    <student>
       <rollNo>3</rollNo>
       <fName>Norm</fName>
       <lName>Walsh</lName>
    </student>
    <student>
       <rollNo>4</rollNo>
       <fName>Michael</fName>
       <lName>Sperberg-McQueen</lName>
    </student>
    <student>
       <rollNo>5</rollNo>
       <fName>Florent</fName>
       <lName>Georges</lName>
    </student>
</students>

I wish to transform, the above XML data into HTML, using XSLT. The resulting HTML, needs to have a table containing rows representing each XML input "student" element, and a total record count at the bottom of HTML output.

Below are my various XSLT solutions,

(1) An XSLT 2.0 solution, with sorting (sorting by fName & lName):

<?xml version="1.0"?>
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform <http://www.w3.org/1999/XSL/Transform>">

    <xsl:output method="html" indent="yes"/>

    <xsl:template match="students">
       <html>
         <head>
            <title>Student list</title>
         </head>
         <body>
            <table>
               <tr>
                  <td><b>Roll No.</b></td>
                  <td><b>First name</b></td>
                  <td><b>Last name</b></td>
               </tr>
               <xsl:for-each select="student">
                  <xsl:sort select="fName"/>
                  <xsl:sort select="lName"/>
                  <tr>
                    <td align="center"><xsl:value-of select="rollNo"/>.</td>
                     <td><xsl:value-of select="fName"/></td>
                     <td><xsl:value-of select="lName"/></td>
                  </tr>
               </xsl:for-each>
               <tr>
         <td colspan="3">&#xa0;</td>
       </tr>
       <tr>
         <td colspan="2"><b>Total no of students</b> : </td>
         <td><xsl:value-of select="count(student)"/></td>
               </tr>
            </table>
         </body>
       </html>
    </xsl:template>

</xsl:stylesheet>

(2) An XSLT 3.0 solution, without sorting:

<?xml version="1.0"?>
<xsl:stylesheet version="3.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform <http://www.w3.org/1999/XSL/Transform>"  xmlns:xs="http://www.w3.org/2001/XMLSchema <http://www.w3.org/2001/XMLSchema>"  exclude-result-prefixes="xs">

    <xsl:output method="html" indent="yes"/>

    <xsl:template match="students">
       <html>
         <head>
            <title>Student list</title>
         </head>
         <body>
            <table>
               <tr>
                  <td><b>Roll No.</b></td>
                  <td><b>First name</b></td>
                  <td><b>Last name</b></td>
               </tr>
               <xsl:iterate select="student">
                  <xsl:param name="total" select="0" as="xs:integer"/>
                  <xsl:on-completion>
                     <tr>
                        <td colspan="3">&#xa0;</td>
                     </tr>
                     <tr>
                       <td colspan="2"><b>Total no of students</b> : </td>
                       <td><xsl:value-of select="$total"/></td>
                     </tr>
                  </xsl:on-completion>
                  <tr>
                    <td align="center"><xsl:value-of select="rollNo"/>.</td>
                     <td><xsl:value-of select="fName"/></td>
                     <td><xsl:value-of select="lName"/></td>
                  </tr>
                  <xsl:next-iteration>
                     <xsl:with-param name="total" select="$total + 1"/>
                  </xsl:next-iteration>
               </xsl:iterate>
            </table>
         </body>
       </html>
    </xsl:template>

</xsl:stylesheet>

(3) An XSLT 3.0 solution, with sorting:

<?xml version="1.0"?>
<xsl:stylesheet version="3.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform <http://www.w3.org/1999/XSL/Transform>"  xmlns:xs="http://www.w3.org/2001/XMLSchema <http://www.w3.org/2001/XMLSchema>"  exclude-result-prefixes="xs">

    <xsl:output method="html" indent="yes"/>

    <xsl:template match="students">
       <html>
         <head>
            <title>Student list</title>
         </head>
         <body>
            <table>
               <tr>
                  <td><b>Roll No.</b></td>
                  <td><b>First name</b></td>
                  <td><b>Last name</b></td>
               </tr>
               <xsl:variable name="result_1" as="element(tr)*">
                  <xsl:iterate select="student">
                     <xsl:param name="total" select="0" as="xs:integer"/>
                     <xsl:on-completion>
                        <tr>
                           <td colspan="3">&#xa0;</td>
                        </tr>
                        <tr>
                         <td colspan="2"><b>Total no of students</b> : </td>
                          <td><xsl:value-of select="$total"/></td>
                        </tr>
                     </xsl:on-completion>
                     <tr>
                       <td align="center"><xsl:value-of select="rollNo"/>.</td>
                        <td><xsl:value-of select="fName"/></td>
                        <td><xsl:value-of select="lName"/></td>
                     </tr>
                     <xsl:next-iteration>
                        <xsl:with-param name="total" select="$total + 1"/>
                     </xsl:next-iteration>
                  </xsl:iterate>
               </xsl:variable>
              <xsl:perform-sort select="$result_1[position() le (count($result_1)-2)]">
                  <xsl:sort select="td[2]"/>
                  <xsl:sort select="td[3]"/>
               </xsl:perform-sort>
              <xsl:copy-of select="$result_1[position() gt (count($result_1)-2)]"/>
            </table>
         </body>
       </html>
    </xsl:template>

</xsl:stylesheet>

I haven't mentioned the solution, where we could use xsl:apply-templates instead of xsl:for-each or xsl:iterate.

Firstly, I find xsl:iterate much more functionally rich (except that it doesn't provide native sorting support) than xsl:for-each, if there's a requirement of XSLT sequential looping. If there's no requirement for sorting, then in XSLT 3.0 environment, I'd opt to use xsl:iterate. If there's requirement for sorting, then in XSLT 3.0 environment, I might opt to use xsl:for-each instead of xsl:iterate (does anybody differ?). When using XSLT 3.0 xsl:iterate, with a requirement of sorting, can anyone suggest a different (and possibly better as well) solution than (3) above?

I agree with Michael that you can always use fn:sort for the select expression of xsl:iterate in XSLT 3 or at least, in Saxon 9.8 and 9.9 HE where the higher-order variant of fn:sort is not available, roll your own sort function with xsl:function and xsl:perform sort that you then call in the select attribute of xsl:iterate.


In general, for that use case, I don't see why xsl:iterate is better than xsl:for-each. I would probably use push style processing with xsl:apply-templates.

Last, for the use with the variable, don't forget that `xsl:perform-sort` can be directly applied to result constructed by nested XSLT so you could also use

             <xsl:perform-sort>
                  <xsl:sort select="td[2]"/>
                  <xsl:sort select="td[3]"/>
                  <xsl:iterate select="student">
                  ...
                  </xsl:iterate>
             </xsl:perform-sort>

perhaps although I guess that will not work with the total column you want to treat differently.

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