com.icl.saxon.expr
Class PathExpression

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

public class PathExpression

extends NodeSetExpression

An expression that establishes a set of nodes by following relationships between nodes in the document. Specifically, it consists of a start expression which defines a set of nodes, and a Step which defines a relationship to be followed from those nodes to create a new set of nodes.

Field Summary

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

staticContext

Constructor Summary

PathExpression(Expression start, Step step)
Constructor

Method Summary

void	display(int level) Diagnostic print of expression structure
NodeEnumeration	enumerate(Context context, boolean sort) Evaluate the path-expression in a given context to return a NodeSet
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

PathExpression

public PathExpression(Expression start,
                      Step step)

Constructor

Parameters:

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

step - The step to be followed from each node in the start expression to yield a new node-set

Method Detail

simplify

public Expression simplify()
                    throws XPathException

Simplify an expression

Overrides:

simplify in class Expression

Returns:

the simplified expression

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 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

enumerate

public NodeEnumeration enumerate(Context context,
                                 boolean sort)
                          throws XPathException

Evaluate the path-expression in a given context to return a NodeSet

Specified by:

enumerate in class NodeSetExpression

Parameters:

context - the evaluation context

sort - true if the returned nodes must be in document order

Throws:

XPathException

display

public void display(int level)

Diagnostic print of expression structure

Specified by:

display in class Expression