com.icl.saxon.expr
Class FilterExpression

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

 class FilterExpression
extends NodeSetExpression

A FilterExpression contains a base expression and a filter predicate, which may be an integer expression (positional filter), or a boolean expression (qualifier)

Field Summary

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

staticContext

Constructor Summary

FilterExpression(Expression start, Expression filter)
Constructor

Method Summary

void	display(int level) Diagnostic print of expression structure
NodeEnumeration	enumerate(Context context, boolean sort) Evaluate the filter expression in a given context to return a Node Enumeration
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 dep, 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

Constructor Detail

FilterExpression

public FilterExpression(Expression start,
                        Expression filter)

Constructor

Parameters:

start - A node-set expression denoting the absolute or relative set of nodes from which the navigation path should start.

filter - An expression defining the filter predicate

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 context,
                                 boolean sort)
                          throws XPathException

Evaluate the filter expression in a given context to return a Node Enumeration

Specified by:

enumerate in class NodeSetExpression

Parameters:

context - the evaluation context

sort - true if the result must be in document order

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

reduce

public Expression reduce(int dep,
                         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:

dep - 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

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

display

public void display(int level)

Diagnostic print of expression structure

Specified by:

display in class Expression