net.sf.saxon.expr

Class InstanceOfExpression

Implemented Interfaces:
EvaluableItem, InstructionInfoProvider, SequenceIterable, Serializable, SourceLocator

public final class InstanceOfExpression
extends UnaryExpression

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

Field Summary

Fields inherited from class net.sf.saxon.expr.UnaryExpression

operand

Fields inherited from class net.sf.saxon.expr.Expression

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD, locationId, staticProperties

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

computeCardinality, computeSpecialProperties, displayExpressionName, displayOperator, equals, explain, getBaseExpression, getItemType, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression, simplify, toString, typeCheck

Methods inherited from class net.sf.saxon.expr.Expression

addToPathMap, adoptChildExpression, checkPermittedContents, computeCardinality, computeDependencies, computeSpecialProperties, computeStaticProperties, copy, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, explain, explain, findParentOf, getCardinality, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getItemType, getLineNumber, getLocationId, getLocationProvider, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, iterate, iterateEvents, iterateSubExpressions, markTailFunctionCalls, optimize, process, promote, replaceSubExpression, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, simplify, staticTypeCheck, suppressValidation, toString, typeCheck, typeError

Constructor Details

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 Details

computeCardinality

public int computeCardinality()
Determine the cardinality
Overrides:
computeCardinality in interface UnaryExpression

copy

public Expression copy()
Copy an expression. This makes a deep copy.
Overrides:
copy in interface Expression
Returns:
the copy of the original expression

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext context)
            throws XPathException
Evaluate the expression as a boolean
Overrides:
effectiveBooleanValue in interface Expression

equals

public boolean equals(Object other)
Is this expression the same as another expression?
Overrides:
equals in interface UnaryExpression

evaluateItem

public Item evaluateItem(XPathContext context)
            throws XPathException
Evaluate the expression
Specified by:
evaluateItem in interface EvaluableItem
Overrides:
evaluateItem in interface 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 interface UnaryExpression

getItemType

public ItemType getItemType(TypeHierarchy th)
Determine the data type of the result of the InstanceOf expression
Overrides:
getItemType in interface UnaryExpression
Parameters:
th - the type hierarchy cache

getRequiredCardinality

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

getRequiredItemType

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

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 interface 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)

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
            throws XPathException
Type-check the expression
Overrides:
typeCheck in interface UnaryExpression
Returns:
the checked expression