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java.lang.Object net.sf.saxon.query.UnboundFunctionLibrary
public class UnboundFunctionLibrary
An UnboundFunctionLibrary is not a real function library; rather, it is used to keep track of function calls that cannot yet be bound to a known declared function, but will have to be bound when all user-declared functions are available.
Constructor Summary | |
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UnboundFunctionLibrary()
Create an XQueryFunctionLibrary |
Method Summary | |
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Expression |
bind(StructuredQName functionName,
Expression[] arguments,
StaticContext env,
Container container)
Identify a (namespace-prefixed) function appearing in the expression. |
void |
bindUnboundFunctionCalls(XQueryFunctionBinder lib,
Configuration config)
Bind function calls that could not be bound when first encountered. |
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. |
SequenceType[] |
getFunctionSignature(StructuredQName functionName,
int arity)
Test whether a function with a given name and arity is available. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public UnboundFunctionLibrary()
Method Detail |
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public SequenceType[] getFunctionSignature(StructuredQName functionName, int arity)
getFunctionSignature
in interface FunctionLibrary
functionName
- the name of the function requiredarity
- The number of arguments. This is set to -1 in the case of the single-argument
public Expression bind(StructuredQName functionName, Expression[] arguments, StaticContext env, Container container) throws XPathException
Note that a function call may appear earlier in the query than the definition of the function to which it is bound. Unlike XSLT, we cannot search forwards to find the function definition. Binding of function calls is therefore a two-stage process; at the time the function call is parsed, we simply register it as pending; subsequently at the end of query parsing all the pending function calls are resolved. Another consequence of this is that we cannot tell at the time a function call is parsed whether it is a call to an internal (XSLT or XQuery) function or to an extension function written in Java.
bind
in interface FunctionLibrary
functionName
- the QName of the function being calledarguments
- 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 callcontainer
- The container for the newly created Expression
XPathException
- if the function call is invalid, either because it is
an unprefixed call to a non-system function, or because it is calling a system
function that is available in XSLT only. A prefixed function call that cannot
be recognized at this stage is assumed to be a forwards reference, and is bound
later when bindUnboundFunctionCalls() is called.public void bindUnboundFunctionCalls(XQueryFunctionBinder lib, Configuration config) throws XPathException
lib
- A library containing all the XQuery functions that have been declared;
the method searches this library for this missing function callconfig
- The Saxon configuration
XPathException
- if a function call refers to a function that has
not been declaredpublic FunctionLibrary copy()
copy
in interface FunctionLibrary
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