com.icl.saxon.expr
Class RootExpression

java.lang.Object
  com.icl.saxon.expr.Expression
      com.icl.saxon.expr.NodeSetExpression
          com.icl.saxon.expr.SingletonExpression
              com.icl.saxon.expr.RootExpression

public class RootExpression

extends SingletonExpression

An expression whose value is always a set of nodes containing a single node, the document root.

Field Summary

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

staticContext

Constructor Summary

RootExpression()

Method Summary

void	display(int level) Diagnostic print of expression structure
boolean	evaluateAsBoolean(Context context) Evaluate as a boolean.
java.lang.String	evaluateAsString(Context context) Evaluate as a string
int	getDependencies() Determine which aspects of the context the expression depends on.
NodeInfo	getNode(Context context) Return the first element selected by this Expression
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.SingletonExpression

enumerate, evaluateAsNodeSet, isContextDocumentNodeSet, selectFirst

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

evaluate, getDataType, outputStringValue

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

RootExpression

public RootExpression()

Method Detail

simplify

public Expression simplify()
                    throws XPathException

Simplify an expression

Overrides:

simplify in class Expression

Returns:

the simplified expression

Throws:

XPathException

getNode

public NodeInfo getNode(Context context)
                 throws XPathException

Return the first element selected by this Expression

Specified by:

getNode in class SingletonExpression

Parameters:

context - The evaluation context

Returns:

the NodeInfo of the first selected element, or null if no element is selected

Throws:

XPathException

evaluateAsString

public java.lang.String evaluateAsString(Context context)
                                  throws XPathException

Evaluate as a string

Overrides:

evaluateAsString in class SingletonExpression

Parameters:

context - The context for evaluation

Returns:

The concatenation of all the character data within the document

Throws:

XPathException

evaluateAsBoolean

public boolean evaluateAsBoolean(Context context)
                          throws XPathException

Evaluate as a boolean.

Overrides:

evaluateAsBoolean in class SingletonExpression

Parameters:

context - The context (not used)

Returns:

true (always - because the nodeset is never empty)

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 dependencies,
                         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:

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

Throws:

XPathException

display

public void display(int level)

Diagnostic print of expression structure

Specified by:

display in class Expression