net.sf.saxon.functions
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, Expression
public class Existence
- extends SystemFunction
Implement the exists() and empty() functions
- See Also:
- Serialized Form
Methods inherited from class net.sf.saxon.expr.ComputedExpression |
computeDependencies, computeSpecialProperties, computeStaticProperties, dynamicError, evaluateAsString, getCardinality, getDependencies, getIntrinsicDependencies, getLineNumber, getSpecialProperties, iterate, markTailFunctionCalls, setLineNumber, typeError |
Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
EXISTS
public static final int EXISTS
- See Also:
- Constant Field Values
EMPTY
public static final int EMPTY
- See Also:
- Constant Field Values
Existence
public Existence()
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