com.icl.saxon.expr
Class EmptyNodeSet

java.lang.Object
  com.icl.saxon.expr.Expression
      com.icl.saxon.expr.Value
          com.icl.saxon.expr.NodeSetValue
              com.icl.saxon.expr.EmptyNodeSet

public final class EmptyNodeSet

extends NodeSetValue

A node-set value no nodes

Field Summary

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

ANY, BOOLEAN, NODESET, NUMBER, OBJECT, STRING

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

staticContext

Constructor Summary

EmptyNodeSet()

Method Summary

boolean	asBoolean() Evaluate as a boolean.
java.lang.String	asString() Convert to string value
NodeEnumeration	enumerate() Return an enumeration of this nodeset value.
boolean	equals(Value other) Test whether this nodeset "equals" another Value
Value	evaluate(Context context) Evaluate the Node Set.
NodeSetValue	evaluateAsNodeSet(Context context) Evaluate an expression as a NodeSet.
int	getCount() Count the nodes in the node-set.
NodeInfo	getFirst() Get the first node in the nodeset (in document order)
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.
boolean	isSorted() Test whether the value is known to be sorted
boolean	notEquals(Value other) Test whether this nodeset "not-equals" another Value
void	setSorted(boolean isSorted) Set a flag to indicate whether the nodes are sorted.
NodeSetValue	sort() Sort the nodes into document order.

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

asNumber, compare, conversionPreference, convertToJava, display, enumerate, getDataType

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

getDependencies, inverse, numericCompare, reduce, simplify, stringToNumber

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

containsReferences, evaluateAsBoolean, evaluateAsNumber, evaluateAsString, getStaticContext, indent, make, outputStringValue, setStaticContext, usesCurrent

Methods inherited from class java.lang.Object

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

Constructor Detail

EmptyNodeSet

public EmptyNodeSet()

Method Detail

evaluate

public Value evaluate(Context context)

Evaluate the Node Set. This guarantees to return the result in sorted order.

Overrides:

evaluate in class NodeSetValue

Parameters:

context - The context for evaluation (not used)

evaluateAsNodeSet

public NodeSetValue evaluateAsNodeSet(Context context)

Evaluate an expression as a NodeSet.

Overrides:

evaluateAsNodeSet in class NodeSetValue

Parameters:

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

Returns:

the value of the expression, evaluated in the current context

setSorted

public void setSorted(boolean isSorted)

Set a flag to indicate whether the nodes are sorted. Used when the creator of the node-set knows that they are already in document order.

Specified by:

setSorted in class NodeSetValue

Parameters:

isSorted - true if the caller wishes to assert that the nodes are in document order and do not need to be further sorted

isSorted

public boolean isSorted()

Test whether the value is known to be sorted

Specified by:

isSorted in class NodeSetValue

Returns:

true if the value is known to be sorted in document order, false if it is not known whether it is sorted.

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

asString

public java.lang.String asString()

Convert to string value

Specified by:

asString in class NodeSetValue

Returns:

an empty string

asBoolean

public boolean asBoolean()

Evaluate as a boolean.

Specified by:

asBoolean in class NodeSetValue

Returns:

false

getCount

public int getCount()

Count the nodes in the node-set.

Specified by:

getCount in class NodeSetValue

Returns:

zero

sort

public NodeSetValue sort()

Sort the nodes into document order. This does nothing if the nodes are already known to be sorted; to force a sort, call setSorted(false)

Specified by:

sort in class NodeSetValue

Returns:

the same NodeSetValue, after sorting. (Historic)

getFirst

public NodeInfo getFirst()

Get the first node in the nodeset (in document order)

Specified by:

getFirst in class NodeSetValue

Returns:

null

equals

public boolean equals(Value other)

Test whether this nodeset "equals" another Value

Overrides:

equals in class NodeSetValue

notEquals

public boolean notEquals(Value other)

Test whether this nodeset "not-equals" another Value

Overrides:

notEquals in class NodeSetValue

enumerate

public NodeEnumeration enumerate()

Return an enumeration of this nodeset value.

Specified by:

enumerate in class NodeSetValue