Class UnionExpression


  • class UnionExpression
    extends NodeSetExpression
    An expression representing a nodeset that is a union of two other NodeSets
    • Constructor Detail

      • UnionExpression

        public UnionExpression​(Expression p1,
                               Expression p2)
        Constructor
        Parameters:
        p1 - the left-hand operand
        p2 - the right-hand operand
    • Method Detail

      • enumerate

        public NodeEnumeration enumerate​(Context c,
                                         boolean sort)
                                  throws XPathException
        Evaluate the union expression. The result will always be sorted in document order, with duplicates eliminated
        Specified by:
        enumerate in class NodeSetExpression
        Parameters:
        c - The context for evaluation
        sort - Request the nodes in document order (they will be, regardless)
        Returns:
        a NodeSetValue representing the union of the two operands
        Throws:
        XPathException - when the expression does not return a nodeset.
      • getDependencies

        public int getDependencies()
        Determine which aspects of the context the expression depends on. The result is a bitwise-or'ed value composed from constants such as Context.VARIABLES and Context.CURRENT_NODE
        Specified by:
        getDependencies in class Expression
      • isContextDocumentNodeSet

        public boolean isContextDocumentNodeSet()
        Determine, in the case of an expression whose data type is Value.NODESET, whether all the nodes in the node-set are guaranteed to come from the same document as the context node. Used for optimization.
        Overrides:
        isContextDocumentNodeSet in class Expression
      • reduce

        public Expression reduce​(int dependencies,
                                 Context context)
                          throws XPathException
        Perform a partial evaluation of the expression, by eliminating specified dependencies on the context.
        Specified by:
        reduce in class Expression
        Parameters:
        dependencies - The dependencies to be removed
        context - The context to be used for the partial evaluation
        Returns:
        a new expression that does not have any of the specified dependencies
        Throws:
        XPathException
      • display

        public void display​(int level)
        Diagnostic print of expression structure
        Specified by:
        display in class Expression