Package net.sf.saxon.expr
Class TailCallLoop
- java.lang.Object
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- net.sf.saxon.expr.ComputedExpression
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- net.sf.saxon.expr.UnaryExpression
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- net.sf.saxon.expr.TailCallLoop
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,Container
,Expression
,InstructionInfoProvider
public final class TailCallLoop extends UnaryExpression
A TailCallLoop wraps the body of a function that contains tail-recursive function calls. On completion of the "real" body of the function it tests whether the function has executed a tail call, and if so, iterates to evaluate the tail call.- See Also:
- Serialized Form
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Field Summary
Fields Modifier and Type Field Description (package private) UserFunction
containingFunction
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Fields inherited from class net.sf.saxon.expr.UnaryExpression
operand
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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 TailCallLoop(UserFunction function)
Constructor
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description protected java.lang.String
displayOperator(Configuration config)
Give a string representation of the operator for use in diagnosticsItem
evaluateItem(XPathContext context)
Evaluate as an Item.int
getImplementationMethod()
An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().ItemType
getItemType(TypeHierarchy th)
Determine the data type of the items returned by the expressionSequenceIterator
iterate(XPathContext context)
Iterate over the sequence of valuesvoid
process(XPathContext context)
Process the function bodyExpression
simplify(StaticContext env)
Simplify an expressionExpression
typeCheck(StaticContext env, ItemType contextItemType)
Type-check the expression-
Methods inherited from class net.sf.saxon.expr.UnaryExpression
computeCardinality, computeSpecialProperties, display, equals, getBaseExpression, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression
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Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, markTailFunctionCalls, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation, typeError
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Field Detail
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containingFunction
UserFunction containingFunction
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Constructor Detail
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TailCallLoop
public TailCallLoop(UserFunction function)
Constructor
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Method Detail
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simplify
public Expression simplify(StaticContext env) throws XPathException
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
public Expression typeCheck(StaticContext env, ItemType contextItemType) throws XPathException
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:
StaticError
- if an error is discovered during this phase (typically a type error)XPathException
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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. This implementation provides both iterate() and process() methods natively.- Specified by:
getImplementationMethod
in interfaceExpression
- Overrides:
getImplementationMethod
in classComputedExpression
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iterate
public SequenceIterator iterate(XPathContext context) throws XPathException
Iterate over the sequence of values- Specified by:
iterate
in interfaceExpression
- Overrides:
iterate
in classComputedExpression
- 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
public Item evaluateItem(XPathContext context) throws XPathException
Evaluate as an Item.- 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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process
public void process(XPathContext context) throws XPathException
Process the function body- Specified by:
process
in interfaceExpression
- Overrides:
process
in classComputedExpression
- Parameters:
context
- The dynamic context, giving access to the current node, the current variables, etc.- Throws:
XPathException
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getItemType
public ItemType getItemType(TypeHierarchy th)
Determine the data type of the items returned by the expression- Specified by:
getItemType
in interfaceExpression
- Overrides:
getItemType
in classUnaryExpression
- Parameters:
th
-- Returns:
- the item type of the items in the result sequence, insofar as this is known statically.
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displayOperator
protected java.lang.String displayOperator(Configuration config)
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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