net.sf.saxon.expr
Class InstanceOfExpression

java.lang.Object
  extended by net.sf.saxon.expr.Expression
      extended by net.sf.saxon.expr.UnaryExpression
          extended by net.sf.saxon.expr.InstanceOfExpression
All Implemented Interfaces:
Serializable, SourceLocator, EvaluableItem, SequenceIterable, InstructionInfoProvider

public final class InstanceOfExpression
extends UnaryExpression

InstanceOf Expression: implements "Expr instance of data-type"

See Also:
Serialized Form

Field Summary
 
Fields inherited from class net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
 
Constructor Summary
InstanceOfExpression(Expression source, SequenceType target)
          Construct an "instance of" expression in the form "source instance of target"
 
Method Summary
 int computeCardinality()
          Determine the cardinality
 Expression copy()
          Copy an expression.
 boolean effectiveBooleanValue(XPathContext context)
          Evaluate the expression as a boolean
 boolean equals(Object other)
          Is this expression the same as another expression?
 Item evaluateItem(XPathContext context)
          Evaluate the expression
 void explain(ExpressionPresenter destination)
          Diagnostic print of expression structure.
 ItemType getItemType(TypeHierarchy th)
          Determine the data type of the result of the InstanceOf expression
 int getRequiredCardinality()
          Get the cardinality that we are testing for membership of
 ItemType getRequiredItemType()
          Get the item type that we are testing for membership of
 Expression optimize(ExpressionVisitor visitor, ItemType contextItemType)
          Perform optimisation of an expression and its subexpressions.
 Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
          Type-check the expression
 
Methods inherited from class net.sf.saxon.expr.UnaryExpression
computeSpecialProperties, getBaseExpression, hashCode, iterateSubExpressions, promote, replaceSubExpression, simplify, toString
 
Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, evaluateAsString, explain, findParentOf, getCardinality, getColumnNumber, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterate, iterateEvents, markTailFunctionCalls, process, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation
 
Methods inherited from class java.lang.Object
getClass, notify, notifyAll, wait, wait, wait
 

Constructor Detail

InstanceOfExpression

public InstanceOfExpression(Expression source,
                            SequenceType target)
Construct an "instance of" expression in the form "source instance of target"

Parameters:
source - the expression whose type is to be tested
target - the type against which it is tested
Method Detail

getRequiredItemType

public ItemType getRequiredItemType()
Get the item type that we are testing for membership of

Returns:
the item type

getRequiredCardinality

public int getRequiredCardinality()
Get the cardinality that we are testing for membership of

Returns:
the required cardinality

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
                     throws XPathException
Type-check the expression

Overrides:
typeCheck in class UnaryExpression
Parameters:
visitor - an expression visitor
contextItemType - 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
Returns:
the checked expression
Throws:
XPathException - if an error is discovered during this phase (typically a type error)

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 class UnaryExpression
Parameters:
visitor - an expression visitor
contextItemType - 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
Returns:
the original expression, rewritten if appropriate to optimize execution
Throws:
XPathException - if an error is discovered during this phase (typically a type error)

equals

public boolean equals(Object other)
Is this expression the same as another expression?

Overrides:
equals in class UnaryExpression

computeCardinality

public int computeCardinality()
Determine the cardinality

Overrides:
computeCardinality in class UnaryExpression
Returns:
the computed cardinality, as one of the values StaticProperty.ALLOWS_ZERO_OR_ONE, StaticProperty.EXACTLY_ONE, StaticProperty.ALLOWS_ONE_OR_MORE, StaticProperty.ALLOWS_ZERO_OR_MORE

copy

public Expression copy()
Copy an expression. This makes a deep copy.

Specified by:
copy in class Expression
Returns:
the copy of the original expression

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the data type of the result of the InstanceOf expression

Overrides:
getItemType in class UnaryExpression
Parameters:
th - the type hierarchy cache
Returns:
the item type of the items in the result sequence, insofar as this is known statically.

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException
Evaluate the expression

Specified by:
evaluateItem in interface EvaluableItem
Overrides:
evaluateItem in class Expression
Parameters:
context - 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

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext context)
                              throws XPathException
Evaluate the expression as a boolean

Overrides:
effectiveBooleanValue in class Expression
Parameters:
context - 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

explain

public void explain(ExpressionPresenter destination)
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

Overrides:
explain in class UnaryExpression
Parameters:
destination - the expression presenter used to display the structure


Copyright (C) Michael H. Kay. All rights reserved.