Implements XPath functions -- each function is derived from Function,
FunctionOneArg, Function2Args, etc, with number-of-arguments checking being
applied mainly at compile time -- this package only implements XPath functions,
XSLT functions are found in the "templates" package.
This class is duplicated for each JAXP subpackage so keep it in sync.
It is package private and therefore is not exposed as part of the JAXP
API.
This code is designed to implement the JAXP 1.1 spec pluggability
feature and is designed to run on JDK version 1.1 and
later, and to compile on JDK 1.2 and onward.