Class Atomizer
- All Implemented Interfaces:
Serializable
,SourceLocator
,LocationProvider
,SaxonLocator
,InstructionInfo
,Locator
- See Also:
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionstatic class
Implement the mapping function. -
Field Summary
Fields inherited from class net.sf.saxon.expr.UnaryExpression
operand
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 -
Method Summary
Modifier and TypeMethodDescriptionaddToPathMap
(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet) Add a representation of this expression to a PathMap.int
Determine the static cardinality of the expressionint
Determine the special properties of this expressioncopy()
Copy an expression.evaluateItem
(XPathContext context) Evaluate as an Item.static ItemType
getAtomizedItemType
(Expression operand, boolean alwaysUntyped, TypeHierarchy th) Compute the type that will result from atomizing the result of a given expressionstatic SequenceIterator
<? extends AtomicValue> getAtomizingIterator
(SequenceIterator base, boolean untyped) Get an iterator that returns the result of atomizing the sequence delivered by the supplied iteratorDiagnostic print of expression structure.int
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().Determine the data type of the items returned by the expression, if possibleboolean
Ask whether it is known that any nodes in the input will always be untypedSequenceIterator
<? extends AtomicValue> iterate
(XPathContext context) Iterate over the sequence of valuesoptimize
(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Perform optimisation of an expression and its subexpressions.void
process
(XPathContext context) Process the instruction, without returning any tail callssimplify
(ExpressionVisitor visitor) Simplify an expressiontypeCheck
(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Type-check the expressionMethods inherited from class net.sf.saxon.expr.UnaryExpression
displayOperator, equals, explain, getBaseExpression, hashCode, iterateSubExpressions, promote, replaceSubExpression, toString
Methods inherited from class net.sf.saxon.expr.Expression
adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, iterateSameFocusSubExpressions, markTailFunctionCalls, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError
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Constructor Details
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Atomizer
Constructor- Parameters:
sequence
- the sequence to be atomized
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Method Details
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getImplementationMethod
public int getImplementationMethod()An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is provided directly. The other methods will always be available indirectly, using an implementation that relies on one of the other methods.- Overrides:
getImplementationMethod
in classExpression
- Returns:
- the implementation method, for example
Expression.ITERATE_METHOD
orExpression.EVALUATE_METHOD
orExpression.PROCESS_METHOD
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simplify
Simplify an expression- Overrides:
simplify
in classUnaryExpression
- Parameters:
visitor
- an expression visitor- Returns:
- the simplified expression
- Throws:
XPathException
- if an error is discovered during expression rewriting
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException Type-check the expression- Overrides:
typeCheck
in classUnaryExpression
- 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 classUnaryExpression
- 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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isUntyped
public boolean isUntyped()Ask whether it is known that any nodes in the input will always be untyped- Returns:
- true if it is known that all nodes in the input will be untyped
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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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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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iterate
Iterate over the sequence of values- Overrides:
iterate
in classExpression
- Parameters:
context
- supplies the context for evaluation- Returns:
- a SequenceIterator that can be used to iterate over the result of the expression
- Throws:
XPathException
- if any dynamic error occurs evaluating the expression
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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.- 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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process
Process the instruction, without returning any tail calls- Overrides:
process
in classExpression
- Parameters:
context
- The dynamic context, giving access to the current node, the current variables, etc.- Throws:
XPathException
- if a dynamic error occurs
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getItemType
Determine the data type of the items returned by the expression, if possible- Overrides:
getItemType
in classUnaryExpression
- Parameters:
th
- the type hierarchy cache- 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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getAtomizedItemType
public static ItemType getAtomizedItemType(Expression operand, boolean alwaysUntyped, TypeHierarchy th) Compute the type that will result from atomizing the result of a given expression- Parameters:
operand
- the given expressionalwaysUntyped
- true if it is known that nodes will always be untypedth
- the type hierarchy cache- Returns:
- the item type of the result of evaluating the operand expression, after atomization
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computeCardinality
public int computeCardinality()Determine the static cardinality of the expression- Overrides:
computeCardinality
in classUnaryExpression
- 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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addToPathMap
Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.The default implementation of this method assumes that an expression does no navigation other than the navigation done by evaluating its subexpressions, and that the subexpressions are evaluated in the same context as the containing expression. The method must be overridden for any expression where these assumptions do not hold. For example, implementations exist for AxisExpression, ParentExpression, and RootExpression (because they perform navigation), and for the doc(), document(), and collection() functions because they create a new navigation root. Implementations also exist for PathExpression and FilterExpression because they have subexpressions that are evaluated in a different context from the calling expression.
- Overrides:
addToPathMap
in classExpression
- Parameters:
pathMap
- the PathMap to which the expression should be addedpathMapNodeSet
- the PathMapNodeSet to which the paths embodied in this expression should be added- Returns:
- the pathMapNodeSet representing the points in the source document that are both reachable by this expression, and that represent possible results of this expression. For an expression that does navigation, it represents the end of the arc in the path map that describes the navigation route. For other expressions, it is the same as the input pathMapNode.
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getAtomizingIterator
public static SequenceIterator<? extends AtomicValue> getAtomizingIterator(SequenceIterator base, boolean untyped) throws XPathException Get an iterator that returns the result of atomizing the sequence delivered by the supplied iterator- Parameters:
base
- the supplied iterator, the input to atomizationuntyped
- this can safely be set to true if it is known that all nodes in the base sequence will be untyped; but it is always OK to set it to false.- Returns:
- an iterator that returns atomic values, the result of the atomization
- Throws:
XPathException
- if a dynamic evaluation error occurs
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getExpressionName
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.- 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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