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:

ExportAgent, Locatable, IdentityComparable

public final class InstanceOfExpression
extends UnaryExpression

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

Field Summary

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

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, MAX_COST, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, UPDATE_METHOD, WATCH_METHOD

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
int	computeCardinality() Determine the cardinality
int	computeHashCode() get HashCode for comparing two expressions.
Expression	copy(RebindingMap rebindings) Copy an expression.
boolean	effectiveBooleanValue(XPathContext context) Evaluate the expression as a boolean
boolean	equals(java.lang.Object other) Is this expression the same as another expression?
BooleanValue	evaluateItem(XPathContext context) Evaluate the expression
void	export(ExpressionPresenter out) Diagnostic print of expression structure.
java.lang.String	getExpressionName() Get a name identifying the kind of expression, in terms meaningful to a user.
int	getImplementationMethod() An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
ItemType	getItemType() Determine the data type of the result of the InstanceOf expression
protected OperandRole	getOperandRole() Get the usage (in terms of streamability analysis) of the single operand
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
UType	getStaticUType(UType contextItemType) Get the static type of the expression as a UType, following precisely the type inference rules defined in the XSLT 3.0 specification.
java.lang.String	getStreamerName() Get the (partial) name of a class that supports streaming of this kind of expression
Expression	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Perform optimisation of an expression and its subexpressions.
java.lang.String	toShortString() Produce a short string identifying the expression for use in error messages
java.lang.String	toString() The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Type-check the expression

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

computeSpecialProperties, displayOperator, getBaseExpression, getOperand, operands, setBaseExpression

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

addToPathMap, adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, dynamicError, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getConstructType, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setFlattened, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, suppressValidation, toPattern, typeCheckChildren, typeError, unordered, verifyParentPointers

Methods inherited from class java.lang.Object

clone, finalize, 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

getOperandRole

protected OperandRole getOperandRole()

Description copied from class: UnaryExpression

Get the usage (in terms of streamability analysis) of the single operand

Specified by:

getOperandRole in class UnaryExpression

Returns:

the operand usage

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,
                            ContextItemStaticInfo contextInfo)
                     throws XPathException

Type-check the expression

Overrides:

typeCheck in class UnaryExpression

Parameters:

visitor - an expression visitor

contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.

Returns:

the checked expression

Throws:

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

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ContextItemStaticInfo contextInfo)
                    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

contextInfo - 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)

getImplementationMethod

public int getImplementationMethod()

An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.

Specified by:

getImplementationMethod in class Expression

Returns:

the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

equals

public boolean equals(java.lang.Object other)

Is this expression the same as another expression?

Overrides:

equals in class UnaryExpression

Parameters:

other - the other operand; the result is false if this is not an Expression

Returns:

true if the other operand is an expression and if it can be determined that the two expressions are equivalent, in the sense that they will always return the same result.

computeHashCode

public int computeHashCode()

get HashCode for comparing two expressions. Note that this hashcode gives the same result for (A op B) and for (B op A), whether or not the operator is commutative.

Overrides:

computeHashCode in class UnaryExpression

Returns:

a computed hash code

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. May also return StaticProperty.ALLOWS_ZERO if the result is known to be an empty sequence, or StaticProperty.ALLOWS_MANY if if is known to return a sequence of length two or more.

copy

public Expression copy(RebindingMap rebindings)

Copy an expression. This makes a deep copy.

Specified by:

copy in class Expression

Parameters:

rebindings - variable references that need to be rebound

Returns:

the copy of the original expression

getItemType

public ItemType getItemType()

Determine the data type of the result of the InstanceOf expression

Overrides:

getItemType in class UnaryExpression

Returns:

the item type of the items in the result sequence, insofar as this is known statically.

getStaticUType

public UType getStaticUType(UType contextItemType)

Get the static type of the expression as a UType, following precisely the type inference rules defined in the XSLT 3.0 specification.

Overrides:

getStaticUType in class Expression

Parameters:

contextItemType - the statically-inferred type of the context item

Returns:

the static item type of the expression according to the XSLT 3.0 defined rules

evaluateItem

public BooleanValue evaluateItem(XPathContext context)
                          throws XPathException

Evaluate the expression

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

getExpressionName

public java.lang.String getExpressionName()

Get a name identifying the kind of expression, in terms meaningful to a user.

Overrides:

getExpressionName in class Expression

Returns:

a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in export() output displaying the expression.

export

public void export(ExpressionPresenter out)
            throws XPathException

Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.

Specified by:

export in interface ExportAgent

Overrides:

export in class UnaryExpression

Parameters:

out - the expression presenter used to display the structure

Throws:

XPathException - if the export fails, for example if an expression is found that won't work in the target environment.

toString

public java.lang.String toString()

The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax

Overrides:

toString in class UnaryExpression

Returns:

a representation of the expression as a string

toShortString

public java.lang.String toShortString()

Produce a short string identifying the expression for use in error messages

Overrides:

toShortString in class UnaryExpression

Returns:

a short string, sufficient to identify the expression

getStreamerName

public java.lang.String getStreamerName()

Get the (partial) name of a class that supports streaming of this kind of expression

Overrides:

getStreamerName in class Expression

Returns:

the partial name of a class that can be instantiated to provide streaming support in Saxon-EE, or null if there is no such class