Class Existence

java.lang.Object

net.sf.saxon.expr.ComputedExpression

net.sf.saxon.expr.FunctionCall

net.sf.saxon.functions.SystemFunction

net.sf.saxon.functions.Existence

All Implemented Interfaces:

Serializable, SourceLocator, Container, Expression, InstructionInfoProvider

public class Existence
extends SystemFunction

Implement the exists() and empty() functions

See Also:

• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
static final int	EMPTY
static final int	EXISTS

Fields inherited from class SystemFunction

operation

Fields inherited from class FunctionCall

argument

Fields inherited from class ComputedExpression

locationId, staticProperties

Fields inherited from interface Expression

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

Constructors

Constructor	Description
Existence()

Method Summary

Modifier and Type	Method	Description
void	checkArguments(StaticContext env)	Static analysis: prevent sorting of the argument
boolean	effectiveBooleanValue(XPathContext c)	Evaluate the function in a boolean context
Item	evaluateItem(XPathContext c)	Evaluate in a general context

Methods inherited from class SystemFunction

addContextDocumentArgument, computeCardinality, computeSpecialProperties, display, getDetails, getErrorCodeForTypeErrors, getItemType, getRequiredType, main, makeSystemFunction, setDetails, useContextItemAsDefault

Methods inherited from class FunctionCall

checkArgumentCount, getArguments, getDisplayName, getFunctionNameCode, getNumberOfArguments, iterateSubExpressions, optimize, preEvaluate, promote, replaceSubExpression, setArguments, setFunctionNameCode, simplify, simplifyArguments, typeCheck

Methods inherited from class ComputedExpression

adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, evaluateAsString, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, iterate, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation, typeError

Methods inherited from class Object

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

Field Details

EXISTS

public static final int EXISTS

See Also:

• Constant Field Values

EMPTY

public static final int EMPTY

See Also:

• Constant Field Values

Constructor Details

Existence

public Existence()

Method Details

checkArguments

public void checkArguments(StaticContext env)
                    throws XPathException

Static analysis: prevent sorting of the argument

Overrides:

checkArguments in class SystemFunction

Throws:

XPathException

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext c)
                              throws XPathException

Evaluate the function in a boolean context

Specified by:

effectiveBooleanValue in interface Expression

Overrides:

effectiveBooleanValue in class ComputedExpression

Parameters:

c - The context in which the expression is to be evaluated

Returns:

the effective boolean value

Throws:

XPathException - if any dynamic error occurs evaluating the expression

evaluateItem

public Item evaluateItem(XPathContext c)
                  throws XPathException

Evaluate in a general context

Specified by:

evaluateItem in interface Expression

Overrides:

evaluateItem in class ComputedExpression

Parameters:

c - The context in which the expression is to be evaluated

Returns:

the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence

Throws:

XPathException - if any dynamic error occurs evaluating the expression