Package net.sf.saxon.expr
Class SingletonAtomizer
java.lang.Object
net.sf.saxon.expr.ComputedExpression
net.sf.saxon.expr.UnaryExpression
net.sf.saxon.expr.SingletonAtomizer
- All Implemented Interfaces:
Serializable
,SourceLocator
,Container
,Expression
,InstructionInfoProvider
A SingletonAtomizer combines the functions of an Atomizer and a CardinalityChecker: it is used to
atomize a sequence of nodes, checking that the result of the atomization contains zero or one atomic
values. Note that the input may be a sequence of nodes or atomic values, even though the result must
contain at most one atomic value.
- See Also:
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Field Summary
Fields inherited from class net.sf.saxon.expr.UnaryExpression
operand
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
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Constructor Summary
ConstructorsConstructorDescriptionSingletonAtomizer
(Expression sequence, RoleLocator role, boolean allowEmpty) Constructor -
Method Summary
Modifier and TypeMethodDescriptionint
Determine the static cardinality of the expressionint
Determine the special properties of this expressionprotected String
displayOperator
(Configuration config) Give a string representation of the operator for use in diagnosticsevaluateItem
(XPathContext context) Evaluate as an Item.Determine the data type of the items returned by the expression, if possiblegetRole()
Get the RoleLocator (used to construct error messages)simplify
(StaticContext env) Simplify an expressiontypeCheck
(StaticContext env, ItemType contextItemType) Type-check the expressionMethods inherited from class net.sf.saxon.expr.UnaryExpression
display, equals, getBaseExpression, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, 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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Constructor Details
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SingletonAtomizer
Constructor- Parameters:
sequence
- the sequence to be atomizedallowEmpty
- true if the result sequence is allowed to be empty.
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Method Details
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simplify
Simplify an expression- Specified by:
simplify
in interfaceExpression
- Overrides:
simplify
in classUnaryExpression
- Parameters:
env
- the static context- Returns:
- the simplified expression
- Throws:
XPathException
- if an error is discovered during expression rewriting
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typeCheck
Type-check the expression- Specified by:
typeCheck
in interfaceExpression
- Overrides:
typeCheck
in classUnaryExpression
- 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:
XPathException
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computeSpecialProperties
public int computeSpecialProperties()Determine the special properties of this expression- Overrides:
computeSpecialProperties
in classUnaryExpression
- Returns:
StaticProperty.NON_CREATIVE
.
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getRole
Get the RoleLocator (used to construct error messages) -
evaluateItem
Evaluate as an Item. This should only be called if the Atomizer has cardinality zero-or-one, which will only be the case if the underlying expression has cardinality zero-or-one.- Specified by:
evaluateItem
in interfaceExpression
- Overrides:
evaluateItem
in classComputedExpression
- 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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getItemType
Determine the data type of the items returned by the expression, if possible- Specified by:
getItemType
in interfaceExpression
- Overrides:
getItemType
in classUnaryExpression
- Parameters:
th
-- Returns:
- a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER. For this class, the result is always an atomic type, but it might be more specific.
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computeCardinality
public int computeCardinality()Determine the static cardinality of the expression- Overrides:
computeCardinality
in classUnaryExpression
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displayOperator
Give a string representation of the operator for use in diagnostics- Specified by:
displayOperator
in classUnaryExpression
- Parameters:
config
-- Returns:
- the operator, as a string
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