Random sorting and output of random elements in XSLT

Introduction

In this article I want to share with you my attempts to create a random (although it would be more appropriate to say pseudo-random) sorting with XSLT, without using third-party applications and extensions.

Initially, the task was to do the sorting for a PHP XSLT processor. But I wanted to do something more universal.

Prototype

First we need a sample to test the sorting. We will not be engaged in artful designs and we will write simply.
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Data file data.xml

<?xml version="1.0" encoding="UTF-8"?> <?xml-stylesheet type="text/xsl" href="view.xsl"?> <root> <item id="1"/><item id="2"/><item id="3"/><item id="4"/><item id="5"/><item id="6"/><item id="7"/><item id="8"/><item id="9"/><item id="10"/> </root> 

We generate randomness

In order to randomly sort something, you need to have something random at hand. And nothing is better than the generate-id () function, which returns the unique identifier of an element as a string.

Let's see what we get with different processors that were at hand.

View.xsl conversion file

 <?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:output method="html"/> <xsl:template match="/"> <xsl:for-each select="/root/item"> <xsl:value-of select="generate-id()"/><br/> </xsl:for-each> </xsl:template> </xsl:stylesheet> 

Result

Php	Firefox	Opera	Msxml	Safari
id1690783	id0xfd238240	op5275038	IDAKA0MB	idp100503080
id1690785	id0xfd2383d0	op5275022	IDAMA0MB	idp100502144
id1690788	id0xfd238470	op5275006	IDAOA0MB	idp100502072
id1690789	id0xfd2384c0	op5274990	IDAQA0MB	idp100502936
id1690787	id0xfd238510	op5274974	IDASA0MB	idp100502792
id1690784	id0xfd2640b0	op5274958	IDAUA0MB	idp100502648
id1690782	id0xfd2641f0	op5274942	IDAWA0MB	idp125378088
id1690779	id0xfd264240	op5274926	IDAYA0MB	idp100502504
id1690777	id0xfd264330	op5274910	IDA0A0MB	idp125377944
id1690775	id0xfd2643d0	op5274894	IDA2A0MB	idp100503224

Looking at the table, you can see two troubles: the identifiers go in a certain order and each XSLT processor generates an identifier under its own way. I can not write about melkomyagkih, and then stood out.

Random sort

I will not describe my unsuccessful attempts to transform the sequence into randomness, test different algorithms, the amount of alcohol drunk and sleepless nights. I will write what happened as a result.

View.xsl conversion file

 <?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:output method="html"/> <xsl:template match="/"> <xsl:for-each select="/root/item"> <xsl:sort select="translate(generate-id(), 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ', '0192834765019283476501928347650192834765019283476501') mod 3.1415" data-type="number"/> <xsl:value-of select="@id"/><br/> </xsl:for-each> </xsl:template> </xsl:stylesheet> 

The main element here is the “select” attribute of the “xsl: sort” element. So let's proceed to the analysis: the unique identifier of the current element is taken (using the “generate-id ()” function), all alphabetic values ​​are replaced with digital values ​​(using the “translate ()” function) and the result is divided by the module by the Pi number ( why it was Pi, what first came to mind).

Although not pulling on the perfect and elegant solution, it works.

The output of a certain number of random elements.

We modify the table to display a certain number of random elements from the set. The function of determining the number of the current position () element will help us in this. Let's deduce 4 random elements.

View.xsl conversion file

 <?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:output method="html"/> <xsl:template match="/"> <xsl:for-each select="/root/item"> <xsl:sort select="translate(generate-id(), 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ', '0192834765019283476501928347650192834765019283476501') mod 3.1415" data-type="number"/> <xsl:if test="position() &lt; 5"> <xsl:value-of select="@id"/><br/> </xsl:if> </xsl:for-each> </xsl:template> </xsl:stylesheet>. 

Some PHP

Since at the beginning of the article it was mentioned about PHP, then I’ll finish with code for conversion in this language.

 <?php $data = new DOMDocument('1.0', 'UTF-8'); $data->load('data.xml'); $view = new DOMDocument('1.0', 'UTF-8'); $view->load('view.xsl'); $xsl = new XSLTProcessor(); $xsl->importStyleSheet($view); echo $xsl->transformToXML($data); ?>