com.saxonica.expr
Class EquivalenceComparison

java.lang.Object
  net.sf.saxon.expr.Expression
      net.sf.saxon.expr.BinaryExpression
          com.saxonica.expr.EquivalenceComparison

All Implemented Interfaces:

Serializable, SourceLocator, LocationProvider, SaxonLocator, ComparisonExpression, EvaluableItem, SequenceIterable, InstructionInfo, Locator

public class EquivalenceComparison
extends BinaryExpression
implements ComparisonExpression

Class to handle equivalence comparisons of singletons. This only handles equality comparison. It follows the rules used for grouping and for XQuery 1.1 switch expressions: - each operand must be zero or one atomic values - untypedAtomic is treated as string - non-comparable values are not equal (no type errors) - two empty sequences are equal to each other - two NaN values are equal to each other

See Also:

Serialized Form

Field Summary

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

operand0, operand1, operator

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

EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, PUSH_SELECTION, staticProperties, WATCH_METHOD

Constructor Summary

EquivalenceComparison(Expression p1, int operator, Expression p2)
Create a singleton comparison - that is, a comparison between two singleton (0:1) sequences using the general comparison semantics

Method Summary

int	computeCardinality() Determine the static cardinality.
boolean	convertsUntypedToOther() Determine whether untyped atomic values should be converted to the type of the other operand
Expression	copy() Copy an expression.
boolean	effectiveBooleanValue(XPathContext context) Evaluate the expression in a boolean context
Item	evaluateItem(XPathContext context) Evaluate the expression in a given context
protected void	explainExtraAttributes(ExpressionPresenter out) Add subclass-specific attributes to the expression tree explanation.
AtomicComparer	getAtomicComparer() Get the AtomicComparer used to compare atomic values.
ItemType	getItemType(TypeHierarchy th) Determine the data type of the expression
int	getSingletonOperator() Get the primitive (singleton) operator used: one of Token.FEQ, Token.FNE, Token.FLT, Token.FGT, Token.FLE, Token.FGE
Expression	typeCheck(ExpressionVisitor visitor, ItemType contextItemType) Type-check the expression.

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

computeSpecialProperties, displayOperator, equals, explain, getOperands, getOperator, hashCode, isAssociative, isCommutative, isInverse, iterateSubExpressions, optimize, promote, replaceSubExpression, setFlattened, simplify, toString

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

addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getExpressionName, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setLocationId, staticTypeCheck, suppressValidation, typeError

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.sf.saxon.expr.ComparisonExpression

getOperands

Constructor Detail

EquivalenceComparison

public EquivalenceComparison(Expression p1,
                             int operator,
                             Expression p2)

Create a singleton comparison - that is, a comparison between two singleton (0:1) sequences using the general comparison semantics

Parameters:

p1 - the first operand

operator - the operator

p2 - the second operand

Method Detail

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
                     throws XPathException

Type-check the expression. Default implementation for binary operators that accept any kind of operand

Overrides:

typeCheck in class BinaryExpression

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 to perform necessary run-time type checks, and to perform other type-related optimizations

Throws:

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

getAtomicComparer

public AtomicComparer getAtomicComparer()

Description copied from interface: ComparisonExpression

Get the AtomicComparer used to compare atomic values. This encapsulates any collation that is used

Specified by:

getAtomicComparer in interface ComparisonExpression

getSingletonOperator

public int getSingletonOperator()

Description copied from interface: ComparisonExpression

Get the primitive (singleton) operator used: one of Token.FEQ, Token.FNE, Token.FLT, Token.FGT, Token.FLE, Token.FGE

Specified by:

getSingletonOperator in interface ComparisonExpression

convertsUntypedToOther

public boolean convertsUntypedToOther()

Determine whether untyped atomic values should be converted to the type of the other operand

Specified by:

convertsUntypedToOther in interface ComparisonExpression

Returns:

true if untyped values should be converted to the type of the other operand, false if they should be converted to strings.

computeCardinality

public int computeCardinality()

Determine the static cardinality. Returns [1..1]

Overrides:

computeCardinality in class BinaryExpression

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

getItemType

public ItemType getItemType(TypeHierarchy th)

Determine the data type of the expression

Specified by:

getItemType in class Expression

Parameters:

th - the type hierarchy cache

Returns:

Type.BOOLEAN

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

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate the expression in a given context

Specified by:

evaluateItem in interface EvaluableItem

Overrides:

evaluateItem in class Expression

Parameters:

context - the given context for evaluation

Returns:

a BooleanValue representing the result of the numeric comparison of the two operands

Throws:

XPathException - if any dynamic error occurs evaluating the expression

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext context)
                              throws XPathException

Evaluate the expression in a boolean context

Overrides:

effectiveBooleanValue in class Expression

Parameters:

context - the given context for evaluation

Returns:

a boolean representing the result of the numeric comparison of the two operands

Throws:

XPathException - if any dynamic error occurs evaluating the expression

explainExtraAttributes

protected void explainExtraAttributes(ExpressionPresenter out)

Description copied from class: BinaryExpression

Add subclass-specific attributes to the expression tree explanation. Default implementation does nothing; this is provided for subclasses to override.

Overrides:

explainExtraAttributes in class BinaryExpression

Parameters:

out - the output destination for the displayed expression tree