Package net.sf.saxon.functions
Class Existence
- java.lang.Object
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- net.sf.saxon.expr.Expression
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- net.sf.saxon.expr.FunctionCall
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- net.sf.saxon.functions.SystemFunction
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- net.sf.saxon.functions.Existence
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,LocationProvider
,SaxonLocator
,EvaluableItem
,Negatable
,SequenceIterable
,InstructionInfo
,org.xml.sax.Locator
public class Existence extends SystemFunction implements Negatable
Implement the exists() and empty() functions- See Also:
- Serialized Form
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Field Summary
Fields Modifier and Type Field Description static int
EMPTY
static int
EXISTS
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Fields inherited from class net.sf.saxon.functions.SystemFunction
operation
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Fields inherited from class net.sf.saxon.expr.FunctionCall
argument
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Fields inherited from class net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties
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Constructor Summary
Constructors Constructor Description Existence()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
checkArguments(ExpressionVisitor visitor)
Static analysis: prevent sorting of the argumentboolean
effectiveBooleanValue(XPathContext c)
Evaluate the function in a boolean contextItem
evaluateItem(XPathContext c)
Evaluate in a general contextboolean
isNegatable(ExpressionVisitor visitor)
Check whether this specific instance of the expression is negatableExpression
negate()
Return the negation of the expressionExpression
optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.-
Methods inherited from class net.sf.saxon.functions.SystemFunction
addContextDocumentArgument, addDocToPathMap, computeCardinality, computeSpecialProperties, copy, getDetails, getErrorCodeForTypeErrors, getItemType, getRequiredType, makeSystemFunction, setDetails, useContextItemAsDefault
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Methods inherited from class net.sf.saxon.expr.FunctionCall
addExternalFunctionCallToPathMap, checkArgumentCount, equals, explain, getArguments, getDisplayName, getFunctionName, getNumberOfArguments, hashCode, iterateSubExpressions, preEvaluate, promote, replaceSubExpression, setArguments, setFunctionName, simplify, simplifyArguments, toString, typeCheck
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Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, dynamicError, evaluateAsString, evaluatePendingUpdates, explain, findParentOf, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isUpdatingExpression, iterate, iterateEvents, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError
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Field Detail
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EXISTS
public static final int EXISTS
- See Also:
- Constant Field Values
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EMPTY
public static final int EMPTY
- See Also:
- Constant Field Values
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Method Detail
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checkArguments
public void checkArguments(ExpressionVisitor visitor) throws XPathException
Static analysis: prevent sorting of the argument- Overrides:
checkArguments
in classSystemFunction
- Parameters:
visitor
- the expression visitor- Throws:
XPathException
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optimize
public Expression optimize(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
Perform optimisation of an expression and its subexpressions.This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.
- Overrides:
optimize
in classSystemFunction
- Parameters:
visitor
- an expression visitorcontextItemType
- the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set toType.ITEM_TYPE
- Returns:
- the original expression, rewritten if appropriate to optimize execution
- Throws:
XPathException
- if an error is discovered during this phase (typically a type error)
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isNegatable
public boolean isNegatable(ExpressionVisitor visitor)
Check whether this specific instance of the expression is negatable- Specified by:
isNegatable
in interfaceNegatable
- Returns:
- true if it is
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negate
public Expression negate()
Return the negation of the expression
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effectiveBooleanValue
public boolean effectiveBooleanValue(XPathContext c) throws XPathException
Evaluate the function in a boolean context- Overrides:
effectiveBooleanValue
in classExpression
- 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
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evaluateItem
public Item evaluateItem(XPathContext c) throws XPathException
Evaluate in a general context- Specified by:
evaluateItem
in interfaceEvaluableItem
- Overrides:
evaluateItem
in classExpression
- 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
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