Booleans: To Be or Not to Be

Chapter 11 - XPath Data Types and Functions
XSLT For Dummies
by Richard Wagner
Hungry Minds 2002

  

The final major data type XSLT deals with is boolean, which is a simple binary state (true or false). The four built-in functions for boolean values are: not() , true() , false() , and boolean() .

Returning the opposite value

To return a value thats opposite from the one you have, you can use the not() function:

  boolean  not(boolean) 

The following xsl:if instruction evaluates to true if the myvar variable is not true:

 <xsl:if test="not($myvar)"> This was not true. </xsl:if> 

Returning true and false values

To return a true value (no, not the hardware store), use the true() function:

   boolean   true() 

To return a false value, use the false() function:

   boolean   false() 

Converting to a boolean

You can convert a value to a boolean with the boolean() function. A string and node returns true when it is not empty, whereas a number is true if it is not equal to . The syntax is:

  boolean  boolean(object) 

    

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