5.4. Boolean Core Function Group
The Boolean core function group deals with all four kinds of XPath objects, however, the results are always converted to a Boolean. The Boolean functions build upon principles that lay at the core of all programming languages, prepositional logic and artificial intelligence. Boolean functions serve as binary operators—true or false—that act as switches in the course of an XPath function expression. They determine whether a given context's content meets a specific criteria and, depending upon the outcome and syntax, whether the evaluation of the expression will continue.
All five Boolean functions have a function return type of Boolean. Accordingly, they are discussed in order, with respect to the type of arguments ...
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