com.icl.saxon.expr
Class FilterExpression

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

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