net.sf.saxon.expr

Class GeneralComparison

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.BinaryExpression

net.sf.saxon.expr.GeneralComparison

All Implemented Interfaces:

Callable, ComparisonExpression, ExportAgent, Locatable, IdentityComparable

Direct Known Subclasses:

GeneralComparison20, GeneralComparisonEE

public abstract class GeneralComparison
extends BinaryExpression
implements ComparisonExpression, Callable

GeneralComparison: a boolean expression that compares two expressions for equals, not-equals, greater-than or less-than. This implements the operators =, !=, <, >, etc. This implementation is not used when in backwards-compatible mode

Field Summary

Fields

Modifier and Type	Field and Description
protected AtomicComparer	comparer
protected int	comparisonCardinality
protected boolean	doneWarnings
static int	MANY_TO_MANY
static int	MANY_TO_ONE
protected boolean	needsRuntimeCheck
static int	ONE_TO_ONE
protected int	singletonOperator

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

operator

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
GeneralComparison(Expression p0, int op, Expression p1) Create a relational expression identifying the two operands and the operator

Method Summary

Modifier and Type	Method and Description
BooleanValue	call(XPathContext context, Sequence[] arguments) Evaluate the expression
static boolean	compare(AtomicValue a0, int operator, AtomicValue a1, AtomicComparer comparer, boolean checkTypes, XPathContext context, NamespaceResolver nsResolver) Compare two atomic values
int	computeCardinality() Determine the static cardinality.
boolean	convertsUntypedToOther() Determine whether untyped atomic values should be converted to the type of the other operand
boolean	effectiveBooleanValue(XPathContext context) Evaluate the expression in a boolean context
boolean	equals(java.lang.Object other) Is this expression the same as another expression?
BooleanValue	evaluateItem(XPathContext context) Evaluate the expression in a given context
boolean	evaluateManyToMany(SequenceIterator iter0, SequenceIterator iter1, XPathContext context) Evaluate a (zero-or-one)-to-(zero-or-one) comparison
protected void	explainExtraAttributes(ExpressionPresenter out) Add subclass-specific attributes to the expression tree explanation.
AtomicComparer	getAtomicComparer() Get the AtomicComparer used to compare atomic values.
int	getComparisonCardinality() Ask whether the comparison is known to be many-to-one, one-to-one, or many-to-many.
static int	getCorrespondingSingletonOperator(int op) Return the singleton form of the comparison operator, e.g.
java.lang.String	getExpressionName() Get a name identifying the kind of expression, in terms meaningful to a user.
int	getIntrinsicDependencies() Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions.
protected GeneralComparison	getInverseComparison()
ItemType	getItemType() Determine the data type of the expression
NamespaceResolver	getNamespaceResolver() Get the namespace context for this expression, needed in the event that one operand contains untyped atomic values and the other contains QNames
int	getSingletonOperator() Get the primitive (singleton) operator used: one of Token.FEQ, Token.FNE, Token.FLT, Token.FGT, Token.FLE, Token.FGE
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
boolean	needsRuntimeCheck() Ask whether a runtime check of the types of the operands is needed
Expression	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Optimize the expression
void	setAtomicComparer(AtomicComparer comparer) Set the comparer to be used
void	setComparisonCardinality(int card) Say whether the comparison is known to be many-to-one, one-to-one, or many-to-many.
void	setNeedsRuntimeCheck(boolean needsCheck) Say whether a runtime check of the types of the operands is needed
java.lang.String	tag() Get the element name used to identify this expression in exported expression format
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Type-check the expression

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

computeHashCode, computeSpecialProperties, displayOperator, export, getImplementationMethod, getLhs, getLhsExpression, getOperandRole, getOperator, getRhs, getRhsExpression, isAssociative, isCommutative, isInverse, operands, setFlattened, setLhsExpression, setRhsExpression, toShortString, toString

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

addToPathMap, adoptChildExpression, allowExtractingCommonSubexpressions, checkedOperands, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, copy, dynamicError, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getConfiguration, getConstructType, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getInterpretedExpression, 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, 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

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

getLhs, getLhsExpression, getRhs, getRhsExpression

Field Detail

ONE_TO_ONE

public static final int ONE_TO_ONE

See Also:

Constant Field Values

MANY_TO_ONE

public static final int MANY_TO_ONE

See Also:

Constant Field Values

MANY_TO_MANY

public static final int MANY_TO_MANY

See Also:

Constant Field Values

singletonOperator

protected int singletonOperator

comparer

protected AtomicComparer comparer

needsRuntimeCheck

protected boolean needsRuntimeCheck

comparisonCardinality

protected int comparisonCardinality

doneWarnings

protected boolean doneWarnings

Constructor Detail

GeneralComparison

public GeneralComparison(Expression p0,
                         int op,
                         Expression p1)

Create a relational expression identifying the two operands and the operator

Parameters:

p0 - the left-hand operand

op - the operator, as a token returned by the Tokenizer (e.g. Token.LT)

p1 - the right-hand operand

Method Detail

needsRuntimeCheck

public boolean needsRuntimeCheck()

Ask whether a runtime check of the types of the operands is needed

Returns:

true if the types of the operands need to be checked at run-time

setNeedsRuntimeCheck

public void setNeedsRuntimeCheck(boolean needsCheck)

Say whether a runtime check of the types of the operands is needed

Parameters:

needsCheck - true if the types of the operands need to be checked at run-time

getComparisonCardinality

public int getComparisonCardinality()

Ask whether the comparison is known to be many-to-one, one-to-one, or many-to-many. (Note, an expression that is one-to-many will be converted to one that is many-to-one).

Returns:

the Cardinality of the comparison as one of the values ONE_TO_ONE, MANY_TO_MANY, MANY_TO_ONE

setComparisonCardinality

public void setComparisonCardinality(int card)

Say whether the comparison is known to be many-to-one, one-to-one, or many-to-many.

Parameters:

card - the Cardinality of the comparison as one of the values ONE_TO_ONE, MANY_TO_MANY, MANY_TO_ONE

setAtomicComparer

public void setAtomicComparer(AtomicComparer comparer)

Set the comparer to be used

Parameters:

comparer - the comparer to be used

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 explain() output displaying the expression.

getNamespaceResolver

public NamespaceResolver getNamespaceResolver()

Get the namespace context for this expression, needed in the event that one operand contains untyped atomic values and the other contains QNames

getAtomicComparer

public AtomicComparer getAtomicComparer()

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()

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. 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.

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                            ContextItemStaticInfo contextInfo)
                     throws XPathException

Type-check the expression

Overrides:

typeCheck in class BinaryExpression

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)

getIntrinsicDependencies

public int getIntrinsicDependencies()

Description copied from class: Expression

Determine the intrinsic dependencies of an expression, that is, those which are not derived from the dependencies of its subexpressions. For example, position() has an intrinsic dependency on the context position, while (position()+1) does not. The default implementation of the method returns 0, indicating "no dependencies".

Overrides:

getIntrinsicDependencies in class Expression

Returns:

a set of bit-significant flags identifying the "intrinsic" dependencies. The flags are documented in class net.sf.saxon.value.StaticProperty

equals

public boolean equals(java.lang.Object other)

Description copied from class: BinaryExpression

Is this expression the same as another expression?

Overrides:

equals in class BinaryExpression

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.

optimize

public Expression optimize(ExpressionVisitor visitor,
                           ContextItemStaticInfo contextInfo)
                    throws XPathException

Optimize the expression

Overrides:

optimize in class BinaryExpression

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 checked expression

Throws:

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

evaluateItem

public BooleanValue evaluateItem(XPathContext context)
                          throws XPathException

Evaluate the expression in a given context

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

call

public BooleanValue call(XPathContext context,
                         Sequence[] arguments)
                  throws XPathException

Evaluate the expression

Specified by:

call in interface Callable

Parameters:

context - the dynamic evaluation context

arguments - the values of the arguments, supplied as SequenceIterators

Returns:

the result of the evaluation, in the form of a SequenceIterator

Throws:

XPathException - if a dynamic error occurs during the evaluation of 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

evaluateManyToMany

public boolean evaluateManyToMany(SequenceIterator iter0,
                                  SequenceIterator iter1,
                                  XPathContext context)
                           throws XPathException

Evaluate a (zero-or-one)-to-(zero-or-one) comparison

Parameters:

iter0 - iterator over the first value

iter1 - iterator the second value

context - dynamic evaluation context

Returns:

the comparison result

Throws:

XPathException - if a dynamic error occurs

compare

public static boolean compare(AtomicValue a0,
                              int operator,
                              AtomicValue a1,
                              AtomicComparer comparer,
                              boolean checkTypes,
                              XPathContext context,
                              NamespaceResolver nsResolver)
                       throws XPathException

Compare two atomic values

Parameters:

a0 - the first value

operator - the singleton version of the comparison operator, for example Token.FEQ

a1 - the second value

comparer - the comparer to be used to perform the comparison. If the comparer is context-sensitive then the context must already have been bound using comparer.provideContext().

checkTypes - set to true if the operand types need to be checked for comparability at runtime

context - the XPath evaluation context

nsResolver - namespace resolver

Returns:

true if the comparison succeeds

Throws:

XPathException - if a dynamic error occurs during the comparison

getItemType

public ItemType getItemType()

Determine the data type of the expression

Specified by:

getItemType in class Expression

Returns:

the value BuiltInAtomicType.BOOLEAN

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 - static information about the context item

Returns:

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

getCorrespondingSingletonOperator

public static int getCorrespondingSingletonOperator(int op)

Return the singleton form of the comparison operator, e.g. FEQ for EQUALS, FGT for GT

Parameters:

op - the many-to-many form of the operator, for example Token.LE

Returns:

the corresponding singleton operator, for example Token.FLE

getInverseComparison

protected GeneralComparison getInverseComparison()

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

tag

public java.lang.String tag()

Get the element name used to identify this expression in exported expression format

Overrides:

tag in class BinaryExpression

Returns:

the element name used to identify this 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