net.sf.saxon.value
Class ShareableSequence

java.lang.Object
  net.sf.saxon.value.Value
      net.sf.saxon.value.ShareableSequence

All Implemented Interfaces:

Expression, java.io.Serializable, ValueRepresentation

public final class ShareableSequence

extends Value

A sequence value implemented extensionally using an extensible List whose leading part can be shared with other sequence values. The list can be appended to by other users (at most one other user!), but the items within the range used by this sequence value cannot be modified.

See Also:

Serialized Form

Field Summary

Fields inherited from class net.sf.saxon.value.Value

EMPTY_CLASS_ARRAY

Fields inherited from interface net.sf.saxon.expr.Expression

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Fields inherited from interface net.sf.saxon.om.ValueRepresentation

EMPTY_VALUE_ARRAY

Constructor Summary

ShareableSequence(java.util.List list)
Construct an sequence from an array of items.

Method Summary

boolean	effectiveBooleanValue(XPathContext context) Get the effective boolean value
int	getCardinality() Determine the cardinality
int	getImplementationMethod() An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
ItemType	getItemType(TypeHierarchy th) Get the (lowest common) item type
int	getLength() Get the number of items in the sequence
java.util.List	getList() Get the underlying list
boolean	isShareable() Determine whether another value can share this list.
Item	itemAt(int n) Get the n'th item in the sequence (starting with 0 as the first item)
SequenceIterator	iterate(XPathContext context) Return an iterator over this sequence.
Value	reduce() Reduce a value to its simplest form.
Value	simplify() Simplify this value

Methods inherited from class net.sf.saxon.value.Value

asItem, asIterator, asValue, checkPermittedContents, collapseWhitespace, convert, convertJavaObjectToXPath, convertToJava, display, equals, evaluateAsString, evaluateItem, getDependencies, getIterator, getParentExpression, getSpecialProperties, getStringValue, hashCode, iterateSubExpressions, makeQNameValue, normalizeWhitespace, optimize, process, promote, schemaEquals, simplify, stringToNumber, toString, trimWhitespace, typeCheck

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

ShareableSequence

public ShareableSequence(java.util.List list)

Construct an sequence from an array of items. Note, the list of items is used as is, which means the caller must not subsequently change its contents; however it is permitted to subsequently append items to the list (indeed, that is the raison d'etre of this class)

Parameters:

list - the list of items to be included in the sequence

Method Detail

isShareable

public boolean isShareable()

Determine whether another value can share this list. This is true provided the list has not already been extended by another value.

getList

public java.util.List getList()

Get the underlying list

getImplementationMethod

public int getImplementationMethod()

An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is preferred.

simplify

public Value simplify()

Simplify this value

reduce

public Value reduce()

Reduce a value to its simplest form. If the value is a closure or some other form of deferred value such as a FunctionCallPackage, then it is reduced to a SequenceExtent. If it is a SequenceExtent containing a single item, then it is reduced to that item. One consequence that is exploited by class FilterExpression is that if the value is a singleton numeric value, then the result will be an instance of NumericValue

Overrides:

reduce in class Value

getLength

public int getLength()

Get the number of items in the sequence

Overrides:

getLength in class Value

Returns:

the number of items in the sequence

getCardinality

public int getCardinality()

Determine the cardinality

Specified by:

getCardinality in interface Expression

Overrides:

getCardinality in class Value

Returns:

the cardinality of the sequence, using the constants defined in net.sf.saxon.value.Cardinality

See Also:

Cardinality

getItemType

public ItemType getItemType(TypeHierarchy th)

Get the (lowest common) item type

Specified by:

getItemType in interface Expression

Overrides:

getItemType in class Value

Parameters:

th -

Returns:

integer identifying an item type to which all the items in this sequence conform

itemAt

public Item itemAt(int n)

Get the n'th item in the sequence (starting with 0 as the first item)

Overrides:

itemAt in class Value

Parameters:

n - the position of the required item

Returns:

the n'th item in the sequence

iterate

public SequenceIterator iterate(XPathContext context)

Return an iterator over this sequence.

Parameters:

context - dynamic evaluation context; not used in this implementation of the method

Returns:

the required SequenceIterator, positioned at the start of the sequence

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext context)
                              throws XPathException

Get the effective boolean value

Specified by:

effectiveBooleanValue in interface Expression

Overrides:

effectiveBooleanValue in class Value

Parameters:

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

Returns:

the effective boolean value

Throws:

XPathException - if any dynamic error occurs evaluating the expression