com.icl.saxon.expr
Class NodeSetExpression

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

Direct Known Subclasses:

NodeListExpression, PathExpression, SingletonExpression, SortedSelection

public abstract class NodeSetExpression

extends Expression

A NodeSetExpression is any expression denoting a set of nodes.
This is an abstract class, the methods are defaults which may be overridden in subclasses

Field Summary

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

staticContext

Constructor Summary

NodeSetExpression()

Method Summary

abstract NodeEnumeration	enumerate(Context context, boolean sorted) Return a node enumeration.
Value	evaluate(Context context) Evaluate this node-set.
boolean	evaluateAsBoolean(Context context) Evaluate as a boolean.
NodeSetValue	evaluateAsNodeSet(Context context) Evaluate an expression as a NodeSet.
java.lang.String	evaluateAsString(Context context) Evaluate as a string.
int	getDataType() Determine the data type of the exprssion, if possible
void	outputStringValue(Outputter out, Context context) Evaluate an expression as a String and write the result to the specified outputter.
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.Expression

containsReferences, display, evaluateAsNumber, getDependencies, getStaticContext, indent, isContextDocumentNodeSet, 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

NodeSetExpression

public NodeSetExpression()

Method Detail

enumerate

public abstract NodeEnumeration enumerate(Context context,
                                          boolean sorted)
                                   throws XPathException

Return a node enumeration. All NodeSetExpressions must implement this method: the evaluate() function is defined in terms of it. (But note that some expressions that return node-sets are not NodeSetExpressions: for example functions such as key(), id(), and document() are not, and neither are variable references).

Overrides:

enumerate in class Expression

Parameters:

context - The evaluation context

sorted - True if the nodes must be returned in document order

Throws:

XPathException - when the expression does not return a nodeset.

evaluate

public Value evaluate(Context context)
               throws XPathException

Evaluate this node-set. This doesn't actually retrieve all the nodes: it returns a wrapper around a node-set expression in which all context dependencies have been eliminated.

Specified by:

evaluate in class Expression

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

selectFirst

public NodeInfo selectFirst(Context context)
                     throws XPathException

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

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

evaluateAsString

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

Evaluate as a string. Returns the string value of the first node selected by the NodeSetExpression

Overrides:

evaluateAsString in class Expression

Parameters:

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

Returns:

the value of the NodeSetExpression, evaluated in the current context

Throws:

XPathException

outputStringValue

public void outputStringValue(Outputter out,
                              Context context)
                       throws TransformerException

Evaluate an expression as a String and write the result to the specified outputter.

Overrides:

outputStringValue in class Expression

Parameters:

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

out - The required outputter

Returns:

the value of the expression, evaluated in the current context

Throws:

TransformerException

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 Expression

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

evaluateAsNodeSet

public NodeSetValue evaluateAsNodeSet(Context context)
                               throws XPathException

Evaluate an expression as a NodeSet.

Overrides:

evaluateAsNodeSet in class Expression

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.

getDataType

public int getDataType()

Determine the data type of the exprssion, if possible

Specified by:

getDataType in class Expression

Returns:

Value.NODESET