net.sf.saxon.expr
Class TailCallLoop

java.lang.Object
  extended by net.sf.saxon.expr.ComputedExpression
      extended by net.sf.saxon.expr.UnaryExpression
          extended by net.sf.saxon.expr.TailCallLoop
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

Field Summary
(package private)  UserFunction containingFunction
           
 
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
 
Constructor Summary
TailCallLoop(UserFunction function)
          Constructor
 
Method Summary
protected  java.lang.String displayOperator(Configuration config)
          Give a string representation of the operator for use in diagnostics
 Item 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 expression
 SequenceIterator iterate(XPathContext context)
          Iterate over the sequence of values
 void process(XPathContext context)
          Process the function body
 Expression simplify(StaticContext env)
          Simplify an expression
 Expression 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
 
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
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

containingFunction

UserFunction containingFunction
Constructor Detail

TailCallLoop

public TailCallLoop(UserFunction function)
Constructor

Method Detail

simplify

public Expression simplify(StaticContext env)
                    throws XPathException
Simplify an expression

Specified by:
simplify in interface Expression
Overrides:
simplify in class UnaryExpression
Parameters:
env - the static context
Returns:
the simplified expression
Throws:
XPathException - if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(StaticContext env,
                            ItemType contextItemType)
                     throws XPathException
Type-check the expression

Specified by:
typeCheck in interface Expression
Overrides:
typeCheck in class UnaryExpression
Parameters:
env - the static context of the expression
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:
StaticError - if an error is discovered during this phase (typically a type error)
XPathException

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 interface Expression
Overrides:
getImplementationMethod in class ComputedExpression

iterate

public SequenceIterator iterate(XPathContext context)
                         throws XPathException
Iterate over the sequence of values

Specified by:
iterate in interface Expression
Overrides:
iterate in class ComputedExpression
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 Expression
Overrides:
evaluateItem in class ComputedExpression
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

Specified by:
process in interface Expression
Overrides:
process in class ComputedExpression
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

Specified by:
getItemType in interface Expression
Overrides:
getItemType in class UnaryExpression
Parameters:
th -
Returns:
the item type of the items in the result sequence, insofar as this is known statically.

displayOperator

protected java.lang.String displayOperator(Configuration config)
Give a string representation of the operator for use in diagnostics

Specified by:
displayOperator in class UnaryExpression
Parameters:
config -
Returns:
the operator, as a string