com.icl.saxon.expr
Class SingletonExpression

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

Direct Known Subclasses:

ContextNodeExpression, ParentNodeExpression, RootExpression

public abstract class SingletonExpression
extends NodeSetExpression

A node set expression that will always return zero or one nodes

Field Summary

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

staticContext

Constructor Summary

SingletonExpression()

Method Summary

NodeEnumeration	enumerate(Context context, boolean sort) Evaluate the expression in a given context to return a Node enumeration
boolean	evaluateAsBoolean(Context context) Evaluate as a boolean.
NodeSetValue	evaluateAsNodeSet(Context context) Evaluate an expression as a NodeSet.
String	evaluateAsString(Context context) Evaluate as a string.
abstract NodeInfo	getNode(Context context) Get the single node to which this expression refers
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.
NodeInfo	selectFirst(Context context) Return the first node selected by this Expression when evaluated in the current context

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

evaluate, getDataType, outputStringValue

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

containsReferences, display, evaluateAsNumber, getDependencies, getStaticContext, indent, make, reduce, setStaticContext, simplify, usesCurrent

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SingletonExpression

public SingletonExpression()

Method Detail

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

getNode

public abstract NodeInfo getNode(Context context)
                          throws XPathException

Get the single node to which this expression refers

Throws:

XPathException

selectFirst

public NodeInfo selectFirst(Context context)
                     throws XPathException

Return the first node selected by this Expression when evaluated in the current context

Overrides:

selectFirst in class NodeSetExpression

Parameters:

context - The context for the evaluation

Returns:

the NodeInfo of the first node in document order, or null if the node-set is empty.

Throws:

XPathException

enumerate

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

Evaluate the expression in a given context to return a Node enumeration

Specified by:

enumerate in class NodeSetExpression

Parameters:

context - the evaluation context

sort - Indicates result must be in document order

Throws:

XPathException - when the expression does not return a nodeset.

evaluateAsNodeSet

public NodeSetValue evaluateAsNodeSet(Context context)
                               throws XPathException

Evaluate an expression as a NodeSet.

Overrides:

evaluateAsNodeSet 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 - when the expression does not return a nodeset.

evaluateAsString

public String evaluateAsString(Context context)
                        throws XPathException

Evaluate as a string. Returns the string value of the node if it exists

Overrides:

evaluateAsString in class NodeSetExpression

Parameters:

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

Returns:

true if there are any nodes selected by the NodeSetExpression

Throws:

XPathException

evaluateAsBoolean

public boolean evaluateAsBoolean(Context context)
                          throws XPathException

Evaluate as a boolean. Returns true if there are any nodes selected by the NodeSetExpression

Overrides:

evaluateAsBoolean in class NodeSetExpression

Parameters:

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

Returns:

true if there are any nodes selected by the NodeSetExpression

Throws:

XPathException