Package net.sf.saxon.expr
Class ValueComparison
- java.lang.Object
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- net.sf.saxon.expr.Expression
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- net.sf.saxon.expr.BinaryExpression
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- net.sf.saxon.expr.ValueComparison
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,LocationProvider
,SaxonLocator
,ComparisonExpression
,Negatable
,InstructionInfo
,org.xml.sax.Locator
public final class ValueComparison extends BinaryExpression implements ComparisonExpression, Negatable
ValueComparison: a boolean expression that compares two atomic values for equals, not-equals, greater-than or less-than. Implements the operators eq, ne, lt, le, gt, ge- See Also:
- Serialized Form
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Field Summary
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Fields inherited from class net.sf.saxon.expr.BinaryExpression
operand0, operand1, operator
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Fields inherited from class net.sf.saxon.expr.Expression
EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD
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Constructor Summary
Constructors Constructor Description ValueComparison(Expression p1, int op, Expression p2)
Create a comparison expression identifying the two operands and the operator
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description (package private) static boolean
compare(AtomicValue v0, int op, AtomicValue v1, AtomicComparer comparer, boolean checkTypes)
Compare two atomic values, using a specified operator and collationint
computeCardinality()
Determine the static cardinality.boolean
convertsUntypedToOther()
Determine whether untyped atomic values should be converted to the type of the other operandExpression
copy()
Copy an expression.boolean
effectiveBooleanValue(XPathContext context)
Evaluate the effective boolean value of the expressionItem
evaluateItem(XPathContext context)
Evaluate the expression in a given contextprotected void
explainExtraAttribute(ExpressionPresenter out)
AtomicComparer
getAtomicComparer()
Get the AtomicComparer used to compare atomic values.java.lang.String
getExpressionName()
Get a name identifying the kind of expression, in terms meaningful to a user.ItemType
getItemType(TypeHierarchy th)
Determine the data type of the expressionBooleanValue
getResultWhenEmpty()
Get the result to be returned if one of the operands is an empty sequenceint
getSingletonOperator()
Get the primitive (singleton) operator used: one of Token.FEQ, Token.FNE, Token.FLT, Token.FGT, Token.FLE, Token.FGEboolean
isNegatable(ExpressionVisitor visitor)
Check whether this specific instance of the expression is negatableboolean
needsRuntimeComparabilityCheck()
Determine whether a run-time check is needed to check that the types of the arguments are comparableExpression
negate()
Return the negation of this value comparison: that is, a value comparison that returns true() if and only if the original returns false().Expression
optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)
Perform optimisation of an expression and its subexpressions.void
setAtomicComparer(AtomicComparer comparer)
Set the AtomicComparer used to compare atomic valuesvoid
setResultWhenEmpty(BooleanValue value)
Set the result to be returned if one of the operands is an empty sequenceExpression
typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType)
Type-check the expression-
Methods inherited from class net.sf.saxon.expr.BinaryExpression
computeSpecialProperties, displayOperator, equals, explain, explainExtraAttributes, getArguments, getOperands, getOperator, hashCode, isAssociative, isCommutative, isInverse, iterateSubExpressions, promote, replaceSubExpression, setFlattened, simplify, toString
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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, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setLocationId, staticTypeCheck, suppressValidation, typeError
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Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
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Methods inherited from interface net.sf.saxon.expr.ComparisonExpression
getOperands
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Constructor Detail
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ValueComparison
public ValueComparison(Expression p1, int op, Expression p2)
Create a comparison expression identifying the two operands and the operator- Parameters:
p1
- the left-hand operandop
- the operator, as a token returned by the Tokenizer (e.g. Token.LT)p2
- the right-hand operand
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Method Detail
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getExpressionName
public java.lang.String getExpressionName()
Get a name identifying the kind of expression, in terms meaningful to a user.- Overrides:
getExpressionName
in classExpression
- 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.
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setAtomicComparer
public void setAtomicComparer(AtomicComparer comparer)
Set the AtomicComparer used to compare atomic values- Parameters:
comparer
- the AtomicComparer
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getAtomicComparer
public AtomicComparer getAtomicComparer()
Get the AtomicComparer used to compare atomic values. This encapsulates any collation that is used. Note that the comparer is always known at compile time.- Specified by:
getAtomicComparer
in interfaceComparisonExpression
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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 interfaceComparisonExpression
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convertsUntypedToOther
public boolean convertsUntypedToOther()
Determine whether untyped atomic values should be converted to the type of the other operand- Specified by:
convertsUntypedToOther
in interfaceComparisonExpression
- Returns:
- true if untyped values should be converted to the type of the other operand, false if they should be converted to strings.
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setResultWhenEmpty
public void setResultWhenEmpty(BooleanValue value)
Set the result to be returned if one of the operands is an empty sequence- Parameters:
value
- the result to be returned if an operand is empty. Supply null to mean the empty sequence.
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getResultWhenEmpty
public BooleanValue getResultWhenEmpty()
Get the result to be returned if one of the operands is an empty sequence- Returns:
- BooleanValue.TRUE, BooleanValue.FALSE, or null (meaning the empty sequence)
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needsRuntimeComparabilityCheck
public boolean needsRuntimeComparabilityCheck()
Determine whether a run-time check is needed to check that the types of the arguments are comparable- Returns:
- true if a run-time check is needed
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
Type-check the expression- Overrides:
typeCheck
in classBinaryExpression
- Parameters:
visitor
- an expression visitorcontextItemType
- 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 toType.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)
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optimize
public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) 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 classBinaryExpression
- Parameters:
visitor
- an expression visitorcontextItemType
- 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 toType.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)
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isNegatable
public boolean isNegatable(ExpressionVisitor visitor)
Check whether this specific instance of the expression is negatable- Specified by:
isNegatable
in interfaceNegatable
- Returns:
- true if it is
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negate
public Expression negate()
Return the negation of this value comparison: that is, a value comparison that returns true() if and only if the original returns false(). The result must be the same as not(this) even in the case where one of the operands is ().
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copy
public Expression copy()
Copy an expression. This makes a deep copy.- Specified by:
copy
in classExpression
- Returns:
- the copy of the original expression
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effectiveBooleanValue
public boolean effectiveBooleanValue(XPathContext context) throws XPathException
Evaluate the effective boolean value of the expression- Overrides:
effectiveBooleanValue
in classExpression
- Parameters:
context
- the given context for evaluation- Returns:
- a boolean representing the result of the comparison of the two operands
- Throws:
XPathException
- if any dynamic error occurs evaluating the expression
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compare
static boolean compare(AtomicValue v0, int op, AtomicValue v1, AtomicComparer comparer, boolean checkTypes) throws XPathException
Compare two atomic values, using a specified operator and collation- Parameters:
v0
- the first operandop
- the operator, as defined by constants such asToken.FEQ
orToken.FLT
v1
- the second operandcomparer
- the Collator to be used when comparing stringscheckTypes
-- Returns:
- the result of the comparison: -1 for LT, 0 for EQ, +1 for GT
- Throws:
XPathException
- if the values are not comparable
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evaluateItem
public Item evaluateItem(XPathContext context) throws XPathException
Evaluate the expression in a given context- Overrides:
evaluateItem
in classExpression
- Parameters:
context
- the given context for evaluation- Returns:
- a BooleanValue representing the result of the numeric comparison of the two operands, or null representing the empty sequence
- Throws:
XPathException
- if any dynamic error occurs evaluating the expression
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getItemType
public ItemType getItemType(TypeHierarchy th)
Determine the data type of the expression- Specified by:
getItemType
in classExpression
- Parameters:
th
- the type hierarchy cache- Returns:
- Type.BOOLEAN
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computeCardinality
public int computeCardinality()
Determine the static cardinality.- Overrides:
computeCardinality
in classBinaryExpression
- 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
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explainExtraAttribute
protected void explainExtraAttribute(ExpressionPresenter out)
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