com.icl.saxon.expr
Class UnionExpression

java.lang.Object
  extended bycom.icl.saxon.expr.Expression
      extended bycom.icl.saxon.expr.NodeSetExpression
          extended bycom.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

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