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:

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

Direct Known Subclasses:

GeneralComparison20, GeneralComparisonEE

public class GeneralComparison
extends BinaryExpression
implements ComparisonExpression

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

See Also:

Serialized Form

Field Summary

protected AtomicComparer	comparer
protected boolean	needsRuntimeCheck
protected int	singletonOperator

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

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

Method Summary

protected static boolean	compare(AtomicValue a1, int operator, AtomicValue a2, AtomicComparer comparer, boolean checkTypes, XPathContext context) 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
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.
String	getExpressionName() Get a name identifying the kind of expression, in terms meaningful to a user.
protected GeneralComparison	getInverseComparison()
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	optimize(ExpressionVisitor visitor, ItemType contextItemType) Optimize the expression
void	setAtomicComparer(AtomicComparer comparer) Set the comparer to be used
Expression	simplify(ExpressionVisitor visitor) Simplify an expression
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, promote, replaceSubExpression, setFlattened, 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, 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

Field Detail

singletonOperator

protected int singletonOperator

comparer

protected AtomicComparer comparer

needsRuntimeCheck

protected boolean needsRuntimeCheck

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

setAtomicComparer

public void setAtomicComparer(AtomicComparer comparer)

Set the comparer to be used

Parameters:

comparer - the comparer to be used

simplify

public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException

Description copied from class: BinaryExpression

Simplify an expression

Overrides:

simplify in class BinaryExpression

Parameters:

visitor - an expression visitor

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

getExpressionName

public 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.

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

typeCheck

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

Type-check the expression

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 checked expression

Throws:

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

optimize

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

Optimize the expression

Overrides:

optimize 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 checked expression

Throws:

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

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

compare

protected static boolean compare(AtomicValue a1,
                                 int operator,
                                 AtomicValue a2,
                                 AtomicComparer comparer,
                                 boolean checkTypes,
                                 XPathContext context)
                          throws XPathException

Compare two atomic values

Parameters:

a1 - the first value

operator - the operator, for example Token.EQUALS

a2 - the second value

comparer - the comparer to be used to perform the comparison

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

context - the XPath evaluation context @return true if the comparison succeeds

Throws:

XPathException

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:

the value BuiltInAtomicType.BOOLEAN

getInverseComparison

protected GeneralComparison getInverseComparison()

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