Package net.sf.saxon.expr
Class ValueComparison
- java.lang.Object
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- net.sf.saxon.expr.ComputedExpression
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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
,ComparisonExpression
,Container
,Expression
,InstructionInfoProvider
public final class ValueComparison extends BinaryExpression implements ComparisonExpression
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.ComputedExpression
locationId, staticProperties
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Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
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Constructor Summary
Constructors Constructor Description ValueComparison(Expression p1, int op, Expression p2)
Create a relational 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 v1, int op, AtomicValue v2, AtomicComparer collator)
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 operandprotected java.lang.String
displayOperator()
boolean
effectiveBooleanValue(XPathContext context)
Evaluate the effective boolean value of the expressionItem
evaluateItem(XPathContext context)
Evaluate the expression in a given contextAtomicComparer
getAtomicComparer()
Get the AtomicComparer used to compare atomic values.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.FGEValueComparison
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(Optimizer opt, StaticContext env, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.void
setResultWhenEmpty(BooleanValue value)
Set the result to be returned if one of the operands is an empty sequenceExpression
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
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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
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Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, 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 relational 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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getAtomicComparer
public AtomicComparer getAtomicComparer()
Get the AtomicComparer used to compare atomic values. This encapsulates any collation that is used- 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
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getResultWhenEmpty
public BooleanValue getResultWhenEmpty()
Get the result to be returned if one of the operands is an empty sequence
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typeCheck
public Expression typeCheck(StaticContext env, ItemType contextItemType) throws XPathException
Type-check the expression- Specified by:
typeCheck
in interfaceExpression
- Overrides:
typeCheck
in classBinaryExpression
- Parameters:
env
- the static context of the expressioncontextItemType
- 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:
StaticError
- if an error is discovered during this phase (typically a type error)XPathException
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optimize
public Expression optimize(Optimizer opt, StaticContext env, ItemType 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.
- Specified by:
optimize
in interfaceExpression
- Overrides:
optimize
in classBinaryExpression
- 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 expressioncontextItemType
- 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:
StaticError
- if an error is discovered during this phase (typically a type error)XPathException
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negate
public ValueComparison 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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effectiveBooleanValue
public boolean effectiveBooleanValue(XPathContext context) throws XPathException
Evaluate the effective boolean value of the expression- Specified by:
effectiveBooleanValue
in interfaceExpression
- Overrides:
effectiveBooleanValue
in classComputedExpression
- 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 v1, int op, AtomicValue v2, AtomicComparer collator) throws DynamicError
Compare two atomic values, using a specified operator and collation- Parameters:
v1
- the first operandop
- the operator, as defined by constants such asToken.FEQ
orToken.FLT
v2
- the second operandcollator
- the Collator to be used when comparing strings- Throws:
DynamicError
- 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- Specified by:
evaluateItem
in interfaceExpression
- Overrides:
evaluateItem
in classComputedExpression
- 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 interfaceExpression
- Parameters:
th
-- Returns:
- Type.BOOLEAN
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computeCardinality
public int computeCardinality()
Determine the static cardinality.- Overrides:
computeCardinality
in classBinaryExpression
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displayOperator
protected java.lang.String displayOperator()
- Overrides:
displayOperator
in classBinaryExpression
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