net.sf.saxon.functions
Interface FunctionLibrary
- Serializable
- XQueryFunctionBinder
- ConstructorFunctionLibrary, DotNetExtensionLibrary, ExecutableFunctionLibrary, FunctionLibraryList, ImportedFunctionLibrary, JavaExtensionLibrary, StylesheetFunctionLibrary, SystemFunctionLibrary, UnboundFunctionLibrary, VendorFunctionLibrary, XPathFunctionLibrary, XQueryFunctionLibrary
public interface FunctionLibrary
extends Serializable
A FunctionLibrary handles the binding of function calls in XPath (or XQuery) expressions.
There are a number of implementations of this
class to handle different kinds of function: system functions, constructor functions, vendor-defined
functions, Java extension functions, stylesheet functions, and so on. There is also an implementation
FunctionLibraryList
that allows a FunctionLibrary
to be constructed by combining other FunctionLibrary objects.
Expression | bind(StructuredQName functionName, Expression[] staticArgs, StaticContext env) - Bind an extension function, given the URI and local parts of the function name,
and the list of expressions supplied as arguments.
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FunctionLibrary | copy() - This method creates a copy of a FunctionLibrary: if the original FunctionLibrary allows
new functions to be added, then additions to this copy will not affect the original, or
vice versa.
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boolean | isAvailable(StructuredQName functionName, int arity) - Test whether an extension function with a given name and arity is available.
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bind
public Expression bind(StructuredQName functionName,
Expression[] staticArgs,
StaticContext env)
throws XPathException
Bind an extension function, given the URI and local parts of the function name,
and the list of expressions supplied as arguments. This method is called at compile
time.
functionName
- the QName of the function being calledstaticArgs
- The expressions supplied statically in arguments to the function call.
The length of this array represents the arity of the function. The intention is
that the static type of the arguments (obtainable via getItemType() and getCardinality()) may
be used as part of the binding algorithm. In some cases it may be possible for the function
to be pre-evaluated at compile time, for example if these expressions are all constant values.
The conventions of the XPath language demand that the results of a function depend only on the
values of the expressions supplied as arguments, and not on the form of those expressions. For
example, the result of f(4) is expected to be the same as f(2+2). The actual expression is supplied
here to enable the binding mechanism to select the most efficient possible implementation (including
compile-time pre-evaluation where appropriate).env
- The static context of the function call
- An object representing the function to be called, if one is found;
null if no function was found matching the required name and arity.
XPathException
- if a function is found with the required name and arity, but
the implementation of the function cannot be loaded or used; or if an error occurs
while searching for the function.
copy
public FunctionLibrary copy()
This method creates a copy of a FunctionLibrary: if the original FunctionLibrary allows
new functions to be added, then additions to this copy will not affect the original, or
vice versa.
- a copy of this function library. This must be an instance of the original class.
isAvailable
public boolean isAvailable(StructuredQName functionName,
int arity)
Test whether an extension function with a given name and arity is available. This supports
the function-available() function in XSLT. This method may be called either at compile time
or at run time. If the function library is to be used only in an XQuery or free-standing XPath
environment, this method may throw an UnsupportedOperationException.
functionName
- the qualified name of the function being calledarity
- The number of arguments. This is set to -1 in the case of the single-argument
function-available() function; in this case the method should return true if there is some
- true if a function of this name and arity is available for calling.