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java.lang.Object net.sf.saxon.expr.Expression net.sf.saxon.expr.FunctionCall net.sf.saxon.functions.SystemFunction net.sf.saxon.functions.Aggregate net.sf.saxon.functions.Empty
public class Empty
Implementation of the fn:exists function
Field Summary |
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Fields inherited from class net.sf.saxon.functions.SystemFunction |
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operation |
Fields inherited from class net.sf.saxon.expr.FunctionCall |
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argument |
Fields inherited from class net.sf.saxon.expr.Expression |
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EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD |
Constructor Summary | |
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Empty()
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Method Summary | |
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boolean |
effectiveBooleanValue(XPathContext c)
Evaluate the function in a boolean context |
Item |
evaluateItem(XPathContext context)
Evaluate the function |
int |
getImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). |
boolean |
isNegatable(ExpressionVisitor visitor)
Check whether this specific instance of the expression is negatable |
Expression |
negate()
Return the negation of the expression |
Expression |
optimize(ExpressionVisitor visitor,
ExpressionVisitor.ContextItemType contextItemType)
Perform optimisation of an expression and its subexpressions. |
Methods inherited from class net.sf.saxon.functions.Aggregate |
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checkArguments |
Methods inherited from class net.sf.saxon.functions.SystemFunction |
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addContextDocumentArgument, addDocToPathMap, computeCardinality, computeSpecialProperties, copy, equals, getDetails, getErrorCodeForTypeErrors, getItemType, getOperation, getRequiredType, makeSystemFunction, setDetails, useContextItemAsDefault |
Methods inherited from class net.sf.saxon.expr.FunctionCall |
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addExternalFunctionCallToPathMap, checkArgumentCount, explain, getArguments, getDisplayName, getExpressionName, getFunctionName, getNumberOfArguments, hashCode, iterateSubExpressions, preEvaluate, promote, replaceSubExpression, setArguments, setFunctionName, simplify, simplifyArguments, toString, typeCheck |
Methods inherited from class java.lang.Object |
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clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Constructor Detail |
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public Empty()
Method Detail |
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public int getImplementationMethod()
SystemFunction
getImplementationMethod
in class SystemFunction
Expression.ITERATE_METHOD
or Expression.EVALUATE_METHOD
or
Expression.PROCESS_METHOD
public boolean isNegatable(ExpressionVisitor visitor)
public Expression negate()
public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
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.
optimize
in class SystemFunction
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 to
Type.ITEM_TYPE
XPathException
- if an error is discovered during this phase
(typically a type error)public Item evaluateItem(XPathContext context) throws XPathException
evaluateItem
in class Expression
context
- The context in which the expression is to be evaluated
XPathException
- if any dynamic error occurs evaluating the
expressionpublic boolean effectiveBooleanValue(XPathContext c) throws XPathException
effectiveBooleanValue
in class Expression
c
- The context in which the expression is to be evaluated
XPathException
- if any dynamic error occurs evaluating the
expression
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