Operating With Extreme Caution - XML

In addition to what you've just seen, XPath also allows you to build expressions using simple logical and comparison operators. Consider the following table, which illustrates the common ones with examples:

Operator  What It Means            Example
----------------------------------------------------------------------------
--
=  is 
equal to              item[desc = 'Ginger']
!=           is not equal to     
item[desc != 'Ginger']
is greater than          servings > 2
< 
is less than             servings < 5
=           is greater than 
or equal to servings >= 2
<=           is less than or equal to        servings 
<= 10

Most of these comparison operators are used in conjunction with XSLT's "if" and "choose" tests (note that if you use them in an XSLT stylesheet, the < symbol must be replaced with the pre-defined XML entity < to avoid XML errors.).

You can combine expressions using the "and" and "or" operators,

Operator  Example
----------------------------------------------------------------------------
--




and  desc = 'Ginger' and quantity = '1 tsp'




or        desc = 'Cinnamon' or servings >= 3

Here's an example of how you could apply this in an XSLT stylesheet:

<xsl:template match="/">
<xsl:if test="//item/desc = 'Cinnamon' or //servings 
>= 3">
<xsl:value-of select="//name"/>
</xsl:if>
</xsl:template>

Finally, you can perform arithmetic operations with the various arithmetic operators:

Operator  What It Means            Example
----------------------------------------------------------------------------
--
+  Addition   quantity 
+ 5
-  Subtraction  quantity - 5
*  Multiplication  quantity * 5
div  Division   quantity 
div  5
mod  Modulo   quantity mod 5

Here's an example of how you could apply this in an XSLT stylesheet:

<xsl:template match="/">
Current servings: <xsl:value-of select="//servings"/>
Updated 
servings: <xsl:value-of select="//servings * 6"/>
</xsl:template>

This article copyright Melonfire 2001. All rights reserved.

>>> More XML Articles          >>> More By Vikram Vaswani, (c) Melonfire

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