Boolean functions

[Example 40] <C>

In This stylesheet strings are arguments of boolean() function. A string is true if and only if its length is non-zero. In This stylesheet is text transformed into numbers and then subjected to boolean() function. This stylesheet compares "0" as a string and as a number.This stylesheet uses node-sets as arguments for boolean() function.

[Example 41] <C>

The not function returns true if its argument is false, and false otherwise.

[Example 42] <C>

Functions true() and false() are useful, when some conditions are tested during programming.

[Example 43] <C>

The lang function returns true or false depending on whether the language of the context node as specified by xml:lang attributes is the same as or is a sublanguage of the language specified by the argument string. The language of the context node is determined by the value of the xml:lang attribute on the context node, or, if the context node has no xml:lang attribute, by the value of the xml:lang attribute on the nearest ancestor of the context node that has an xml:lang attribute. If there is no such attribute, then lang returns false. If there is such an attribute, then lang returns true if the attribute value is equal to the argument ignoring case, or if there is some suffix starting with - such that the attribute value is equal to the argument ignoring that suffix of the attribute value and ignoring case.