net.sf.saxon.functions
Class Existence

java.lang.Object
  net.sf.saxon.expr.Expression
      net.sf.saxon.expr.FunctionCall
          net.sf.saxon.functions.SystemFunction
              net.sf.saxon.functions.Existence

All Implemented Interfaces:

Serializable, SourceLocator, Container, EvaluableItem, SequenceIterable, InstructionInfoProvider

public class Existence
extends SystemFunction

Implement the exists() and empty() functions

See Also:

Serialized Form

Field Summary

static int	EMPTY
static int	EXISTS

Fields inherited from class net.sf.saxon.expr.Expression

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

Existence()

Method Summary

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 net.sf.saxon.functions.SystemFunction

computeCardinality, computeSpecialProperties, display, getDetails, getErrorCodeForTypeErrors, getItemType, main, makeSystemFunction, optimize, setDetails

Methods inherited from class net.sf.saxon.expr.FunctionCall

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

Methods inherited from class net.sf.saxon.expr.Expression

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

Methods inherited from class java.lang.Object

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

Field Detail

EXISTS

public static final int EXISTS

See Also:

Constant Field Values

EMPTY

public static final int EMPTY

See Also:

Constant Field Values

Constructor Detail

Existence

public Existence()

Method Detail

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

Overrides:

effectiveBooleanValue in class Expression

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 EvaluableItem

Overrides:

evaluateItem in class Expression

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