TailCallLoop

java.lang.Object
- net.sf.saxon.expr.Expression
- - net.sf.saxon.expr.UnaryExpression
  - - net.sf.saxon.expr.TailCallLoop

All Implemented Interfaces:

java.io.Serializable, javax.xml.transform.SourceLocator, LocationProvider, SaxonLocator, EvaluableItem, SequenceIterable, InstructionInfo, org.xml.sax.Locator
```
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

Field Summary
- Fields inherited from class net.sf.saxon.expr.Expression
  EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties
- Fields inherited from class net.sf.saxon.expr.UnaryExpression
  operand

Constructor Summary

Constructors
Constructor Description

TailCallLoop(UserFunction function)
Constructor - create a TailCallLoop

Constructors
Constructor	Description
`TailCallLoop(UserFunction function)`	Constructor - create a TailCallLoop

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`Expression`	`copy()`	Copy an expression.
`protected java.lang.String`	`displayExpressionName()`	Give a string representation of the expression name for use in diagnostics
`Item`	`evaluateItem(XPathContext context)`	Evaluate as an Item.
`UserFunction`	`getContainingFunction()`	Get the containing function
`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 expression
`SequenceIterator`	`iterate(XPathContext context)`	Iterate over the sequence of values
`void`	`process(XPathContext context)`	Process the function body
`Expression`	`typeCheck(ExpressionVisitor visitor, ItemType contextItemType)`	Type-check the expression

Methods inherited from class net.sf.saxon.expr.Expression
addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeDependencies, computeStaticProperties, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluatePendingUpdates, explain, findParentOf, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasLoopingSubexpression, implementsStaticTypeCheck, isUpdatingExpression, iterateEvents, markTailFunctionCalls, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from class net.sf.saxon.expr.UnaryExpression
computeCardinality, computeSpecialProperties, displayOperator, equals, explain, getBaseExpression, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression, simplify, toString

- Constructor Detail
  - TailCallLoop
```
public TailCallLoop(UserFunction function)
```
    Constructor - create a TailCallLoop
    
    Parameters:
    
    function - the function in which this tail call loop appears
- Method Detail
  - getContainingFunction
```
public UserFunction getContainingFunction()
```
    Get the containing function
    
    Returns:
    
    the containing function
  - typeCheck
```
public Expression typeCheck(ExpressionVisitor visitor,
                            ItemType contextItemType)
                     throws XPathException
```
    Type-check the expression
    
    Overrides:
    
    typeCheck in class UnaryExpression
    
    Parameters:
    
    visitor - an expression visitor
    
    contextItemType - 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 to Type.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)
  - 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.
    
    Overrides:
    
    getImplementationMethod in class Expression
    
    Returns:
    
    the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD
  - copy
```
public Expression copy()
```
    Copy an expression. This makes a deep copy.
    
    Specified by:
    
    copy in class Expression
    
    Returns:
    
    the copy of the original expression
  - iterate
```
public SequenceIterator iterate(XPathContext context)
                         throws XPathException
```
    Iterate over the sequence of values
    
    Specified by:
    
    iterate in interface SequenceIterable
    
    Overrides:
    
    iterate in class Expression
    
    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
  - evaluateItem
```
public Item evaluateItem(XPathContext context)
                  throws XPathException
```
    Evaluate as an Item.
    
    Specified by:
    
    evaluateItem in interface EvaluableItem
    
    Overrides:
    
    evaluateItem in class Expression
    
    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
  - process
```
public void process(XPathContext context)
             throws XPathException
```
    Process the function body
    
    Overrides:
    
    process in class Expression
    
    Parameters:
    
    context - The dynamic context, giving access to the current node, the current variables, etc.
    
    Throws:
    
    XPathException
  - getItemType
```
public ItemType getItemType(TypeHierarchy th)
```
    Determine the data type of the items returned by the expression
    
    Overrides:
    
    getItemType in class UnaryExpression
    
    Parameters:
    
    th - The type hierarchy cache
    
    Returns:
    
    the item type of the items in the result sequence, insofar as this is known statically.
  - displayExpressionName
```
protected java.lang.String displayExpressionName()
```
    Give a string representation of the expression name for use in diagnostics
    
    Overrides:
    
    displayExpressionName in class UnaryExpression
    
    Returns:
    
    the expression name, as a string

Class TailCallLoop

Field Summary

Fields inherited from class net.sf.saxon.expr.Expression

Fields inherited from class net.sf.saxon.expr.UnaryExpression

Constructor Summary

Method Summary

Methods inherited from class net.sf.saxon.expr.Expression

Methods inherited from class java.lang.Object

Methods inherited from class net.sf.saxon.expr.UnaryExpression

Constructor Detail

TailCallLoop

Method Detail

getContainingFunction

typeCheck

getImplementationMethod

copy

iterate

evaluateItem

process

getItemType

displayExpressionName