Class 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
    • 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)
      • 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
      • 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
      • 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