Package net.sf.saxon.expr

Class TailCallLoop

java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.UnaryExpression
net.sf.saxon.expr.TailCallLoop
All Implemented Interfaces:
ExportAgent, Locatable, IdentityComparable, Traceable
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.

  • Constructor Details

    • TailCallLoop

      public TailCallLoop(UserFunction function, Expression body)
      Constructor - create a TailCallLoop
      Parameters:
      function - the function in which this tail call loop appears
      body - the function body (before wrapping in the tail call loop)

  • Method Details

    • getContainingFunction

      public UserFunction getContainingFunction()
      Get the containing function
      Returns:
      the containing function

    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) throws XPathException
      Type-check the expression
      Overrides:
      typeCheck in class UnaryExpression
      Parameters:
      visitor - an expression visitor
      contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.
      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.
      Specified by:
      getImplementationMethod in class Expression
      Returns:
      the implementation method, for example Expression.ITERATE_METHOD or Expression.EVALUATE_METHOD or Expression.PROCESS_METHOD

    • getOperandRole

      protected OperandRole getOperandRole()
      Description copied from class: UnaryExpression
      Get the usage (in terms of streamability analysis) of the single operand
      Specified by:
      getOperandRole in class UnaryExpression
      Returns:
      the operand usage

    • copy

      public Expression copy(RebindingMap rebindings)
      Copy an expression. This makes a deep copy.
      Specified by:
      copy in class Expression
      Parameters:
      rebindings - Variables whose binding needs to change
      Returns:
      the copy of the original expression

    • iterate

      public SequenceIterator iterate(XPathContext context) throws XPathException
      Iterate over the sequence of values
      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.
      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(Outputter output, XPathContext context) throws XPathException
      Process the function body
      Overrides:
      process in class Expression
      Parameters:
      output - the destination for the result
      context - The dynamic context, giving access to the current node,
      Throws:
      XPathException - if a dynamic error occurs

    • getItemType

      public ItemType getItemType()
      Determine the data type of the items returned by the expression
      Overrides:
      getItemType in class UnaryExpression
      Returns:
      the item type of the items in the result sequence, insofar as this is known statically.

    • getExpressionName

      public String getExpressionName()
      Give a string representation of the expression name for use in diagnostics
      Overrides:
      getExpressionName in class Expression
      Returns:
      the expression name, as a string

    • getElaborator

      public Elaborator getElaborator()
      Description copied from class: Expression
      Make an elaborator for this expression
      Overrides:
      getElaborator in class Expression
      Returns:
      an appropriate Elaborator