com.icl.saxon.expr
Class UnionExpression

java.lang.Object
  com.icl.saxon.expr.Expression
      com.icl.saxon.expr.NodeSetExpression
          com.icl.saxon.expr.UnionExpression

 class UnionExpression
extends NodeSetExpression

An expression representing a nodeset that is a union of two other NodeSets

Field Summary

protected Expression	p1
protected Expression	p2

Fields inherited from class com.icl.saxon.expr.Expression

staticContext

Constructor Summary

UnionExpression(Expression p1, Expression p2)
Constructor

Method Summary

void	display(int level) Diagnostic print of expression structure
NodeEnumeration	enumerate(Context c, boolean sort) Evaluate the union expression.
int	getDependencies() Determine which aspects of the context the expression depends on.
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.
Expression	reduce(int dependencies, Context context) Perform a partial evaluation of the expression, by eliminating specified dependencies on the context.
Expression	simplify() Simplify an expression

Methods inherited from class com.icl.saxon.expr.NodeSetExpression

evaluate, evaluateAsBoolean, evaluateAsNodeSet, evaluateAsString, getDataType, outputStringValue, selectFirst

Methods inherited from class com.icl.saxon.expr.Expression

containsReferences, evaluateAsNumber, getStaticContext, indent, make, setStaticContext, usesCurrent

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

p1

protected Expression p1

p2

protected Expression p2

Constructor Detail

UnionExpression

public UnionExpression(Expression p1,
                       Expression p2)

Constructor

Parameters:

p1 - the left-hand operand

p2 - the right-hand operand

Method Detail

simplify

public Expression simplify()
                    throws XPathException

Simplify an expression

Overrides:

simplify in class Expression

Returns:

the simplified expression

Throws:

XPathException

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