net.sf.saxon.expr
Class InstanceOfExpression

java.lang.Object
  net.sf.saxon.expr.Expression
      net.sf.saxon.expr.UnaryExpression
          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