net.sf.saxon.functions

Class ContextItemAccessorFunction

java.lang.Object

net.sf.saxon.om.AbstractItem

net.sf.saxon.functions.AbstractFunction

net.sf.saxon.functions.SystemFunction

net.sf.saxon.functions.ContextAccessorFunction

net.sf.saxon.functions.ContextItemAccessorFunction

All Implemented Interfaces:

Callable, Function, GroundedValue, Item, Sequence

Direct Known Subclasses:

ContextItemAccessorFunction.Number_0, ContextItemAccessorFunction.StringAccessor

public class ContextItemAccessorFunction
extends ContextAccessorFunction

A ContextItemAccessorFunction is a function that takes no arguments, but operates implicitly on the context item. In the case of a dynamic call, the context item that is used is the one at the point where the function item is created. Because these functions depend on the context only, with no additional arguments, the function can be evaluated as soon as the context is bound. The function is therefore replaced at this stage with a constant function, that is, one that always returns the same value.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ContextItemAccessorFunction.Number_0 Subclass of ContextItemAccessorFunction to handle number().
static class	ContextItemAccessorFunction.StringAccessor Subclass of ContextItemAccessorFunction to handle string-length() and normalize-space().

Constructor Summary

Constructors

Constructor and Description
ContextItemAccessorFunction()

Method Summary

Modifier and Type	Method and Description
Function	bindContext(XPathContext context) Bind a context item to appear as part of the function's closure.
Sequence	call(XPathContext context, Sequence[] arguments) Evaluate the expression.
GroundedValue	evaluate(Item item, XPathContext context) Evaluate the function.
Expression	makeContextItemExplicit() Create a system function call on this function in which the context item is supplied as an explicit argument
Expression	makeFunctionCall(Expression[] arguments) Make a static call on this function, with specified arguments.

Methods inherited from class net.sf.saxon.functions.SystemFunction

dependsOnContextItem, dynamicCall, equals, export, exportAdditionalArguments, exportAttributes, fixArguments, getArity, getCardinality, getCompilerName, getContextNode, getDescription, getDetails, getErrorCodeForTypeErrors, getFunctionItemType, getFunctionName, getIntegerBounds, getNetCost, getOperandRoles, getRequiredType, getResultItemType, getResultItemType, getRetainedStaticContext, getSpecialProperties, getStaticBaseUriString, getStreamerName, importAttributes, isTrustedResultType, makeCall, makeFunction, makeOptimizedFunctionCall, resultIfEmpty, setArity, setDetails, setRetainedStaticContext, supplyTypeInformation, typeCheckCaller

Methods inherited from class net.sf.saxon.functions.AbstractFunction

atomize, deepEquals, effectiveBooleanValue, getAnnotations, getStringValue, getStringValueCS, isArray, isMap, makeNewContext, simplify, typeCheck

Methods inherited from class net.sf.saxon.om.AbstractItem

getLength, head, isStreamed, itemAt, iterate, reduce, subsequence

Methods inherited from class java.lang.Object

clone, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface net.sf.saxon.om.Function

iterate

Methods inherited from interface net.sf.saxon.om.Item

head

Methods inherited from interface net.sf.saxon.om.GroundedValue

getLength, head, itemAt, reduce, subsequence

Constructor Detail

ContextItemAccessorFunction

public ContextItemAccessorFunction()

Method Detail

bindContext

public Function bindContext(XPathContext context)
                     throws XPathException

Bind a context item to appear as part of the function's closure. If this method has been called, the supplied context item will be used in preference to the context item at the point where the function is actually called.

Specified by:

bindContext in class ContextAccessorFunction

Parameters:

context - the context to which the function applies. Must not be null.

Throws:

XPathException

evaluate

public GroundedValue evaluate(Item item,
                              XPathContext context)
                       throws XPathException

Evaluate the function. This is done by creating a function of the same name, with the context item as an explicit argument, and evaluating that.

Parameters:

item - the context item

context - XPath dynamic context (not normally used)

Returns:

the result of the function

Throws:

XPathException - in the event of a dynamic error

call

public Sequence call(XPathContext context,
                     Sequence[] arguments)
              throws XPathException

Evaluate the expression. This method is not normally used, but is provided to satisfy the interface.

Specified by:

call in interface Callable

Specified by:

call in interface Function

Overrides:

call in class ContextAccessorFunction

Parameters:

context - the dynamic evaluation context

arguments - the values of the arguments, supplied as Sequences

Returns:

the result of the evaluation, in the form of a Sequence

Throws:

XPathException - if a dynamic error occurs during the evaluation of the expression

makeFunctionCall

public Expression makeFunctionCall(Expression[] arguments)

Make a static call on this function, with specified arguments.

Overrides:

makeFunctionCall in class SystemFunction

Parameters:

arguments - the supplied arguments to the function call. This will always be an empty array, since this is a zero-arity function.

Returns:

This implementation returns a call on the equivalent arity-1 version of the function, supplying "." as an explicit argument.

makeContextItemExplicit

public Expression makeContextItemExplicit()

Create a system function call on this function in which the context item is supplied as an explicit argument

Returns:

an equivalent function call in which the context item is supplied explicitly.