net.sf.saxon.functions

Class Empty

java.lang.Object

net.sf.saxon.om.AbstractItem

net.sf.saxon.functions.AbstractFunction

net.sf.saxon.functions.SystemFunction

net.sf.saxon.functions.Aggregate

net.sf.saxon.functions.Empty

All Implemented Interfaces:

PullEvent, Callable, Function, GroundedValue, Item, Sequence

public class Empty
extends Aggregate

Implementation of the fn:exists function

Constructor Summary

Constructors

Constructor and Description
Empty()

Method Summary

Methods

Modifier and Type	Method and Description
BooleanValue	call(XPathContext context, Sequence[] arguments) Evaluate the expression
ExpressionCompiler	getExpressionCompiler() Return the compiler of the Empty expression
EmptyAdjunct	getStreamingAdjunct() Get a class that supports streamed evaluation of this expression
Expression	makeFunctionCall(Expression[] arguments) Make an expression that either calls this function, or that is equivalent to a call on this function
Expression	makeOptimizedFunctionCall(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo, Expression... arguments) Allow the function to create an optimized call based on the values of the actual arguments

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

equals, export, exportAttributes, getArity, getCardinality, getContextNode, getDescription, getDetails, getErrorCodeForTypeErrors, getFunctionItemType, getFunctionName, getIntegerBounds, getOperandRoles, getRequiredType, getResultItemType, getResultItemType, getRetainedStaticContext, getSpecialProperties, getStaticBaseUriString, importAttributes, makeCall, makeFunction, resultIfEmpty, setArity, setDetails, setRetainedStaticContext, supplyTypeInformation, typeCheckCaller

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

atomize, deepEquals, effectiveBooleanValue, getStringValue, getStringValueCS, isArray, isMap, optimize, simplify, typeCheck

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

getLength, head, 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

Empty

public Empty()

Method Detail

makeOptimizedFunctionCall

public Expression makeOptimizedFunctionCall(ExpressionVisitor visitor,
                                   ContextItemStaticInfo contextInfo,
                                   Expression... arguments)
                                     throws XPathException

Description copied from class: SystemFunction

Allow the function to create an optimized call based on the values of the actual arguments

Overrides:

makeOptimizedFunctionCall in class SystemFunction

Parameters:

visitor - the expression visitor

contextInfo - information about the context item

arguments - the supplied arguments to the function call. Note: modifying the contents of this array should not be attempted, it is likely to have no effect.

Returns:

either a function call on this function, or an expression that delivers the same result, or null indicating that no optimization has taken place

Throws:

XPathException - if an error is detected

call

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

Evaluate the expression

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)

Description copied from class: SystemFunction

Make an expression that either calls this function, or that is equivalent to a call on this function

Overrides:

makeFunctionCall in class SystemFunction

Parameters:

arguments - the supplied arguments to the function call

Returns:

either a function call on this function, or an expression that delivers the same result

getExpressionCompiler

public ExpressionCompiler getExpressionCompiler()

Return the compiler of the Empty expression

Overrides:

getExpressionCompiler in class SystemFunction

Returns:

the relevant ExpressionCompiler

getStreamingAdjunct

public EmptyAdjunct getStreamingAdjunct()

Get a class that supports streamed evaluation of this expression

Overrides:

getStreamingAdjunct in class SystemFunction

Returns:

the relevant StreamingAdjunct, or null if none is available