Class SingletonIntersectExpression

All Implemented Interfaces:
ExportAgent, Locatable, IdentityComparable, Traceable

public class SingletonIntersectExpression extends VennExpression
This expression is equivalent to (A intersect B) in the case where A has cardinality zero-or-one. This is handled as a special case because the standard sort-merge algorithm involves an unnecessary sort on B.
  • Constructor Details

    • SingletonIntersectExpression

      public SingletonIntersectExpression(Expression p1, int op, Expression p2)
      Special case of an intersect expression where the first argument is a singleton
      Parameters:
      p1 - the first argument, always a singleton
      op - the operator, always Token.INTERSECT
      p2 - the second argument
  • Method Details

    • simplify

      public Expression simplify() throws XPathException
      Simplify the expression
      Overrides:
      simplify in class VennExpression
      Returns:
      the simplified expression (or the original if unchanged, or if modified in-situ)
      Throws:
      XPathException - if an error is discovered during expression rewriting
    • optimize

      public Expression optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) throws XPathException
      Perform optimisation of an expression and its subexpressions.

      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 VennExpression
      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(RebindingMap rebindings)
      Copy an expression. This makes a deep copy.
      Overrides:
      copy in class VennExpression
      Parameters:
      rebindings - variables that need to be re-bound
      Returns:
      the copy of the original expression
    • iterate

      public SequenceIterator iterate(XPathContext c) throws XPathException
      Iterate over the value of the expression. The result will always be sorted in document order, with duplicates eliminated
      Overrides:
      iterate in class VennExpression
      Parameters:
      c - The context for evaluation
      Returns:
      a SequenceIterator representing the union of the two operands
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression
    • effectiveBooleanValue

      public boolean effectiveBooleanValue(XPathContext c) throws XPathException
      Get the effective boolean value. In the case of a union expression, this is reduced to an OR expression, for efficiency
      Overrides:
      effectiveBooleanValue in class VennExpression
      Parameters:
      c - The context in which the expression is to be evaluated
      Returns:
      the effective boolean value
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression
    • containsNode

      public static boolean containsNode(SequenceIterator iter, NodeInfo m) throws XPathException
      Ask whether the sequence supplied in the first argument contains the node supplied in the second
      Parameters:
      iter - an iterator over nodes. The iterator will be closed if the node is found.
      m - the node to be tested
      Returns:
      true if (and only if) the sequence contains the node
      Throws:
      XPathException - if evaluating the iterator fails
    • getExpressionName

      public String getExpressionName()
      Description copied from class: VennExpression
      Get a name identifying the kind of expression, in terms meaningful to a user.
      Overrides:
      getExpressionName in class VennExpression
      Returns:
      a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.
    • displayOperator

      protected String displayOperator()
      Display the operator used by this binary expression
      Overrides:
      displayOperator in class BinaryExpression
      Returns:
      String representation of the operator (for diagnostic display only)
    • tag

      protected String tag()
      Get the element name used to identify this expression in exported expression format
      Overrides:
      tag in class VennExpression
      Returns:
      the element name used to identify this expression
    • getElaborator

      public Elaborator getElaborator()
      Make an elaborator for this expression
      Overrides:
      getElaborator in class VennExpression
      Returns:
      a suitable elaborator