com.icl.saxon.expr

Class AxisExpression

java.lang.Object

com.icl.saxon.expr.Expression

com.icl.saxon.expr.NodeSetExpression

com.icl.saxon.expr.AxisExpression

final class AxisExpression
extends NodeSetExpression

An AxisExpression is always obtained by simplifying a PathExpression. It represents a PathExpression that starts at the context node, and uses a simple node-test with no filters. For example "*", "title", "./item", "@*", or "ancestor::chapter*".

Field Summary

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

staticContext

Constructor Summary

Constructors

Constructor and Description
AxisExpression(byte axis, NodeTest nodeTest) Constructor

Method Summary

Methods

Modifier and Type	Method and Description
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
Value	evaluate(Context context) Evaluate the expression (typically used if the result is to be stored in a variable)
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

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

AxisExpression

public AxisExpression(byte axis,
              NodeTest nodeTest)

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()

Simplify an expression

Overrides:

simplify in class Expression

Returns:

the simplified expression

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 - when the expression does not return a nodeset.

evaluate

public Value evaluate(Context context)
               throws XPathException

Evaluate the expression (typically used if the result is to be stored in a variable)

Overrides:

evaluate in class NodeSetExpression

Parameters:

context - The context in which the expression is to be evaluated

Returns:

the value of the expression, evaluated in the current context

Throws:

XPathException

display

public void display(int level)

Diagnostic print of expression structure

Specified by:

display in class Expression