net.sf.saxon.expr

Class GeneralComparison

java.lang.Object

net.sf.saxon.expr.ComputedExpression

net.sf.saxon.expr.BinaryExpression

net.sf.saxon.expr.GeneralComparison

All Implemented Interfaces:

java.io.Serializable, javax.xml.transform.SourceLocator, ComparisonExpression, Container, Expression, InstructionInfoProvider

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

Fields

Modifier and Type	Field and Description
protected AtomicComparer	comparer
protected int	singletonOperator

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

operand0, operand1, operator

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

locationId, staticProperties

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

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_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
protected static boolean	compare(AtomicValue a1, int operator, AtomicValue a2, AtomicComparer comparer, 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
protected java.lang.String	displayOperator()
boolean	effectiveBooleanValue(XPathContext context) Evaluate the expression in a boolean context
Item	evaluateItem(XPathContext context) Evaluate the expression in a given context
AtomicComparer	getAtomicComparer() Get the AtomicComparer used to compare atomic values.
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(Optimizer opt, StaticContext env, ItemType contextItemType) Optimize the expression
Expression	typeCheck(StaticContext env, ItemType contextItemType) Type-check the expression

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

computeSpecialProperties, display, equals, getOperands, getOperator, hashCode, isAssociative, isCommutative, isInverse, iterateSubExpressions, promote, replaceSubExpression, simplify

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

adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, evaluateAsString, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, iterate, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation, typeError

Methods inherited from class java.lang.Object

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

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

getOperands

Field Detail

singletonOperator

protected int singletonOperator

comparer

protected transient AtomicComparer comparer

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

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

typeCheck

public Expression typeCheck(StaticContext env,
                            ItemType contextItemType)
                     throws XPathException

Type-check the expression

Specified by:

typeCheck in interface Expression

Overrides:

typeCheck in class BinaryExpression

Parameters:

env - the static context of the expression

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:

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

XPathException

optimize

public Expression optimize(Optimizer opt,
                           StaticContext env,
                           ItemType contextItemType)
                    throws XPathException

Optimize the expression

Specified by:

optimize in interface Expression

Overrides:

optimize in class BinaryExpression

Parameters:

opt - the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.

env - the static context of the expression

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:

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

XPathException

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate the expression in a given context

Specified by:

evaluateItem in interface Expression

Overrides:

evaluateItem in class ComputedExpression

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

Specified by:

effectiveBooleanValue in interface Expression

Overrides:

effectiveBooleanValue in class ComputedExpression

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,
                                 XPathContext context)
                          throws XPathException

Compare two atomic values

Throws:

XPathException

getItemType

public ItemType getItemType(TypeHierarchy th)

Determine the data type of the expression

Specified by:

getItemType in interface Expression

Parameters:

th -

Returns:

Type.BOOLEAN

getInverseComparison

protected GeneralComparison getInverseComparison()

displayOperator

protected java.lang.String displayOperator()

Overrides:

displayOperator in class BinaryExpression