Class InstanceOfExpression

java.lang.Object

net.sf.saxon.expr.ComputedExpression

net.sf.saxon.expr.UnaryExpression

net.sf.saxon.expr.InstanceOfExpression

All Implemented Interfaces:

Serializable, SourceLocator, Container, Expression, InstructionInfoProvider

public final class InstanceOfExpression
extends UnaryExpression

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

See Also:

• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
(package private) int	targetCardinality
(package private) ItemType	targetType

Fields inherited from class UnaryExpression

operand

Fields inherited from class ComputedExpression

locationId, staticProperties

Fields inherited from interface Expression

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

Constructors

Constructor	Description
InstanceOfExpression(Expression source, SequenceType target)

Method Summary

Modifier and Type	Method	Description
int	computeCardinality()	Determine the cardinality
void	display(int level, PrintStream out, Configuration config)	Diagnostic print of expression structure
protected String	displayOperator(Configuration config)	Give a string representation of the operator for use in diagnostics
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
ItemType	getItemType(TypeHierarchy th)	Determine the data type of the result of the InstanceOf expression
Expression	optimize(Optimizer opt, StaticContext env, ItemType contextItemType)	Perform optimisation of an expression and its subexpressions.
Expression	typeCheck(StaticContext env, ItemType contextItemType)	Type-check the expression

Methods inherited from class UnaryExpression

computeSpecialProperties, getBaseExpression, hashCode, iterateSubExpressions, promote, replaceSubExpression, simplify

Methods inherited from class ComputedExpression

adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, evaluateAsString, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, iterate, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation, typeError

Methods inherited from class Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Field Details

targetType

ItemType targetType

targetCardinality

int targetCardinality

Constructor Details

InstanceOfExpression

public InstanceOfExpression(Expression source,
 SequenceType target)

Method Details

typeCheck

public Expression typeCheck(StaticContext env,
 ItemType contextItemType)
                     throws XPathException

Type-check the expression

Specified by:

typeCheck in interface Expression

Overrides:

typeCheck in class UnaryExpression

Parameters:

env - the static context of the expression

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

optimize

public Expression optimize(Optimizer opt,
 StaticContext env,
 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.

Specified by:

optimize in interface Expression

Overrides:

optimize in class UnaryExpression

Parameters:

opt - the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.

env - the static context of the expression

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:

StaticError - if an error is discovered during this phase (typically a type error)

XPathException

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

getItemType

public ItemType getItemType(TypeHierarchy th)

Determine the data type of the result of the InstanceOf expression

Specified by:

getItemType in interface Expression

Overrides:

getItemType in class UnaryExpression

Parameters:

th -

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 Expression

Overrides:

evaluateItem in class ComputedExpression

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

Specified by:

effectiveBooleanValue in interface Expression

Overrides:

effectiveBooleanValue in class ComputedExpression

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

displayOperator

protected String displayOperator(Configuration config)

Give a string representation of the operator for use in diagnostics

Specified by:

displayOperator in class UnaryExpression

Parameters:

config -

Returns:

the operator, as a string

display

public void display(int level,
 PrintStream out,
 Configuration config)

Diagnostic print of expression structure

Specified by:

display in interface Expression

Overrides:

display in class UnaryExpression

Parameters:

level - indentation level for this expression

out - Output destination

config -