com.icl.saxon.expr

Class UnionExpression


(package private) 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

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

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

containsReferences, display, enumerate, evaluate, evaluateAsBoolean, evaluateAsNodeSet, evaluateAsNumber, evaluateAsString, getDataType, getDependencies, getStaticContext, indent, isContextDocumentNodeSet, make, outputStringValue, reduce, setStaticContext, simplify, usesCurrent

Field Details

p1

protected Expression p1

p2

protected Expression p2

Constructor Details

UnionExpression

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

Method Details

display

public void display(int level)
Diagnostic print of expression structure
Overrides:
display in interface Expression

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
Overrides:
enumerate in interface 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

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
Overrides:
getDependencies in interface 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 interface 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.
Overrides:
reduce in interface 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

simplify

public Expression simplify()
            throws XPathException
Simplify an expression
Overrides:
simplify in interface Expression
Returns:
the simplified expression