Package net.sf.saxon.expr
Class IdentityComparison
java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.BinaryExpression
net.sf.saxon.expr.IdentityComparison
- All Implemented Interfaces:
ExportAgent
,Locatable
,IdentityComparable
,Traceable
IdentityComparison: a boolean expression that compares two nodes
for equals, not-equals, greater-than or less-than based on identity and
document ordering
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionstatic class
Elaborator for an identity comparison (operatorsis
,<<
, and>>
) -
Field Summary
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
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Constructor Summary
ConstructorsConstructorDescriptionIdentityComparison
(Expression p1, int op, Expression p2) Create an identity comparison identifying the two operands and the operator -
Method Summary
Modifier and TypeMethodDescriptioncopy
(RebindingMap rebindings) Copy an expression.protected String
Display the operator used by this binary expressionboolean
effectiveBooleanValue
(XPathContext context) Get the effective boolean value of the expression.evaluateItem
(XPathContext context) Evaluate the expressionMake an elaborator for this expressionGet a name identifying the kind of expression, in terms meaningful to a user.Determine the data type of the expressionprotected OperandRole
getOperandRole
(int arg) Get the operand rolegetStaticUType
(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.boolean
Test the flag that indicates different empty-sequence behavior when emulating comparison of two generate-id'soptimize
(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) Perform optimisation of an expression and its subexpressions.void
setGenerateIdEmulation
(boolean flag) Set flag to indicate different empty-sequence behavior when emulating comparison of two generate-id's.protected String
tag()
Get the element name used to identify this expression in exported expression formattypeCheck
(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Type-check the expressionMethods inherited from class net.sf.saxon.expr.BinaryExpression
computeCardinality, computeHashCode, computeSpecialProperties, equals, explainExtraAttributes, export, getImplementationMethod, getLhs, getLhsExpression, 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, dispatchTailCall, dynamicError, evaluateAsString, explain, getCardinality, getConfiguration, getCost, getDependencies, getEvaluationMethod, getExtraProperty, getIntegerBounds, getIntrinsicDependencies, getLocalRetainedStaticContext, getLocation, getNetCost, getObjectName, getPackageData, getParentExpression, getProperties, getProperty, getRetainedStaticContext, getScopingExpression, getSlotsUsed, getSpecialProperties, getStaticBaseURI, getStaticBaseURIString, getStaticType, getStreamerName, getTracingTag, hasCompatibleStaticContext, hashCode, hasSpecialProperty, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isCallOn, isEqual, isIdentical, isInstruction, isLiftable, isMultiThreaded, isStaticPropertiesKnown, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterate, makeElaborator, markTailFunctionCalls, operandList, operandSparseList, optimizeChildren, prepareForStreaming, process, resetLocalStaticProperties, restoreParentPointers, setEvaluationMethod, setExtraProperty, setFiltered, setLocation, setParentExpression, setRetainedStaticContext, setRetainedStaticContextLocally, setRetainedStaticContextThoroughly, setStaticProperty, simplify, simplifyChildren, staticTypeCheck, supportsLazyEvaluation, suppressValidation, toPattern, typeCheckChildren, typeError, unordered, verifyParentPointers, withLocation
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
Methods inherited from interface net.sf.saxon.trace.Traceable
gatherProperties
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Constructor Details
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IdentityComparison
Create an identity comparison 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 Details
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setGenerateIdEmulation
public void setGenerateIdEmulation(boolean flag) Set flag to indicate different empty-sequence behavior when emulating comparison of two generate-id's. This is relevant when operands evaluate to an empty sequence; if both are empty, the "is" operator returns (), while the generate-id() comparison compares two empty strings, which returns true; if one is empty, the "is" operator returns (), while the generate-id() comparison returns false.- Parameters:
flag
- true if this function is being used to compare generate-id() output
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isGenerateIdEmulation
public boolean isGenerateIdEmulation()Test the flag that indicates different empty-sequence behavior when emulating comparison of two generate-id's- Returns:
- true if this function is being used to compare generate-id() output
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException Type-check the expression- Overrides:
typeCheck
in classBinaryExpression
- Parameters:
visitor
- an expression visitorcontextInfo
- Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.- 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, ContextItemStaticInfo 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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getOperandRole
Description copied from class:BinaryExpression
Get the operand role- Overrides:
getOperandRole
in classBinaryExpression
- Parameters:
arg
- which argument: 0 for the lhs, 1 for the rhs- Returns:
- the operand role
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copy
Copy an expression. This makes a deep copy.- Specified by:
copy
in classExpression
- Parameters:
rebindings
- variables that must be re-bound- Returns:
- the copy of the original expression
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tag
Get the element name used to identify this expression in exported expression format- Overrides:
tag
in classBinaryExpression
- Returns:
- the element name used to identify this expression
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evaluateItem
Evaluate the expression- Overrides:
evaluateItem
in classExpression
- Parameters:
context
- The context in which the expression is to be evaluated- Returns:
- the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
- Throws:
XPathException
- if any dynamic error occurs evaluating the expression
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effectiveBooleanValue
Description copied from class:Expression
Get the effective boolean value of the expression. This returns false if the value is the empty sequence, a zero-length string, a number equal to zero, or the boolean false. Otherwise it returns true.- Overrides:
effectiveBooleanValue
in classExpression
- Parameters:
context
- The context in which the expression is to be evaluated- Returns:
- the effective boolean value
- Throws:
XPathException
- if any dynamic error occurs evaluating the expression
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getItemType
Determine the data type of the expression- Specified by:
getItemType
in classExpression
- Returns:
- Type.BOOLEAN
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getStaticUType
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 classExpression
- Parameters:
contextItemType
- the static type of the context item- Returns:
- the static item type of the expression according to the XSLT 3.0 defined rules
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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 export() output displaying the expression.
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displayOperator
Display the operator used by this binary expression- Overrides:
displayOperator
in classBinaryExpression
- Returns:
- String representation of the operator (for diagnostic display only)
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getElaborator
Make an elaborator for this expression- Overrides:
getElaborator
in classExpression
- Returns:
- a suitable elaborator
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