XSL Basics (part 2) - Be Cool

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The example you just saw used an ordered list to display the items in correct numeric order. Now, while this is fine and dandy so long as you're only outputting HTML, what happens if you suddenly need to output the same data as ASCII text, which doesn't come with a convenient auto-numbering feature?

Well, have no fear - XSLT comes with its own built-in numbering system, accessed via the <xsl:number> instruction. This construct comes in very handy when you need to print a series of sequential numbers, or print numbers in a style different from the standard decimal system.

Let's take a look at how it works, by using the following XML document as source data:

<?xml version="1.0"?>
<bookstore>
<title>Be Cool</title>
<title>Mystic 
River</title>
<title>Hit List</title>
<title>Silent Joe</title>
<title>The 
Travel Detective</title>
</bookstore>

And here's the XSLT stylesheet:

<?xml version="1.0"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template 
match="title">
<xsl:number value="position()"/>
<xsl:value-of select="." 
/>
</xsl:template>
</xsl:stylesheet>

And the output would be:

1Be Cool
2Mystic River
3Hit List
4Silent Joe
5The Travel Detective

In this case, the position of each node in the collection is used as the number.

In case the number format doesn't work for you, you can alter it with the "format" attribute - try the format "I" for Roman numerals, or "a" for alphabetic numbering. The rule

<xsl:template match="title">
<xsl:number value="position()" format="I. 
"/>
<xsl:value-of select="." />
</xsl:template>

returns

I. Be Cool
II. Mystic River
III. Hit List
IV. Silent Joe
V. The Travel Detective

In addition to this simple numbering mechanism, XSLT also allows you to count and display specific types of nodes within the document. For example, if I needed to display a number next to each of the steps in the process below,

<?xml version="1.0"?>
<recipe>
<ingredients>
<item>Boneless 
chicken breasts</item>
<item>Chopped onions</item>
<item>Ginger</item>
</ingredients>
<process>
<step>Cut 
chicken into cubes, wash and apply lime juice and salt</step>
<step>Add 
ginger, garlic, chili, coriander and lime juice in a separate
bowl</step>
<step>Mix 
well, and add chicken to marinate for 3-4 hours</step>
<step>Place chicken 
pieces on skewers and barbeque</step>
<step>Remove, apply butter, and 
barbeque again until meat is tender</step>
<step>Garnish with lemon and 
chopped onions</step>
</process>
</recipe>

I could use the following stylesheet.

<?xml version="1.0"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template 
match="/">
Preparation:
<xsl:apply-templates select="recipe/process" />
</xsl:template>
<xsl:template 
match="process/step">
<xsl:number count="step" format="a. " />
<xsl:value-of 
select="." />
</xsl:template>
</xsl:stylesheet>

Here, the second template rule specifies that only "step" elements are to be counted and numbered. Note, however, that this numbering mechanism only works on nodes at the same level in the node tree - if you'd like to include nodes at other levels, there's an additional "level" attribute you need to use.

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