Class SimpleStepExpression

All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, ContextMappingFunction<Item>, ContextSwitchingExpression, InstructionInfo, Locator

public final class SimpleStepExpression extends SlashExpression
An SimpleStepExpression is a special case of a SlashExpression in which the start expression selects a single item (or nothing), and the step expression is a simple AxisExpression. This is designed to avoid the costs of creating a new dynamic context for expressions (common in XQuery) such as for $b in EXPR return $b/title
See Also:
  • Constructor Details

  • Method Details

    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
      Description copied from class: SlashExpression
      Type-check the expression
      Overrides:
      typeCheck in class SlashExpression
      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)
    • optimize

      public Expression optimize(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
      Description copied from class: Expression
      Perform optimisation of an expression and its subexpressions. This is the third and final phase of static optimization.

      This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.

      Overrides:
      optimize in class SlashExpression
      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 if appropriate to optimize execution
      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.
      Overrides:
      copy in class SlashExpression
      Returns:
      the copy of the original expression
    • iterate

      public SequenceIterator iterate(XPathContext context) throws XPathException
      Evaluate the expression, returning an iterator over the result
      Overrides:
      iterate in class SlashExpression
      Parameters:
      context - the evaluation context
      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