net.sf.saxon.value
Class SequenceExtent

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

All Implemented Interfaces:

Serializable, SequenceIterable, GroundedValue, ValueRepresentation

public final class SequenceExtent
extends Value
implements GroundedValue

A sequence value implemented extensionally. That is, this class represents a sequence by allocating memory to each item in the sequence.

See Also:

Serialized Form

Field Summary

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

INDETERMINATE_ORDERING

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

EMPTY_VALUE_ARRAY

Constructor Summary

SequenceExtent(Item[] items)
Construct an sequence from an array of items.

SequenceExtent(Item[] value, int start, int length)
Construct a SequenceExtent from part of an array of items

SequenceExtent(List list)
Construct a SequenceExtent from a List.

SequenceExtent(SequenceExtent ext, int start, int length)
Construct a SequenceExtent as a view of another SequenceExtent

SequenceExtent(SequenceIterator iter)
Construct a sequence containing all the items in a SequenceIterator.

Method Summary

boolean	effectiveBooleanValue() Get the effective boolean value
int	getCardinality() Determine the cardinality
ItemType	getItemType(TypeHierarchy th) Get the (lowest common) item type
int	getLength() Get the number of items in the sequence
Item	itemAt(int n) Get the n'th item in the sequence (starting with 0 as the first item)
SequenceIterator	iterate() Return an iterator over this sequence.
static ValueRepresentation	makeSequenceExtent(SequenceIterator iter) Factory method to make a Value holding the contents of any SequenceIterator
Value	reduce() Reduce a value to its simplest form.
UnfailingIterator	reverseIterate() Return an enumeration of this sequence in reverse order (used for reverse axes)
Value	simplify() Simplify this SequenceExtent
GroundedValue	subsequence(int start, int length) Get a subsequence of the value
void	swap(int a, int b) Swap two items (needed to support sorting)
String	toString()

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

asItem, asItem, asIterator, asValue, checkPermittedContents, convertToJava, equals, fromItem, getCanonicalLexicalRepresentation, getIterator, getSchemaComparable, getStringValue, getStringValueCS, isIdentical, iterate, process, stringToNumber

Methods inherited from class java.lang.Object

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

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

getStringValue, getStringValueCS

Constructor Detail

SequenceExtent

public SequenceExtent(Item[] items)

Construct an sequence from an array of items. Note, the array of items is used as is, which means the caller must not subsequently change its contents.

Parameters:

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

SequenceExtent

public SequenceExtent(Item[] value,
                      int start,
                      int length)

Construct a SequenceExtent from part of an array of items

Parameters:

value - The array

start - zero-based offset of the first item in the array that is to be included in the new SequenceExtent

length - The number of items in the new SequenceExtent

SequenceExtent

public SequenceExtent(SequenceExtent ext,
                      int start,
                      int length)

Construct a SequenceExtent as a view of another SequenceExtent

Parameters:

ext - The existing SequenceExtent

start - zero-based offset of the first item in the existing SequenceExtent that is to be included in the new SequenceExtent

length - The number of items in the new SequenceExtent

SequenceExtent

public SequenceExtent(List list)

Construct a SequenceExtent from a List. The members of the list must all be Items

Parameters:

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

SequenceExtent

public SequenceExtent(SequenceIterator iter)
               throws XPathException

Construct a sequence containing all the items in a SequenceIterator.

Parameters:

iter - The supplied sequence of items. This must be positioned at the start, so that hasNext() returns true if there are any nodes in the node-set, and next() returns the first node.

Throws:

XPathException - if reading the items using the SequenceIterator raises an error

Method Detail

makeSequenceExtent

public static ValueRepresentation makeSequenceExtent(SequenceIterator iter)
                                              throws XPathException

Factory method to make a Value holding the contents of any SequenceIterator

Parameters:

iter - a Sequence iterator that will be consumed to deliver the items in the sequence

Returns:

a ValueRepresentation holding the items delivered by the SequenceIterator. If the sequence is empty the result will be an instance of EmptySequence. If it is of length one, the result will be an Item. In all other cases, it will be an instance of SequenceExtent.

Throws:

XPathException

simplify

public Value simplify()

Simplify this SequenceExtent

Returns:

a Value holding the items delivered by the SequenceIterator. If the sequence is empty the result will be an instance of EmptySequence. If it is of length one, the result will be an AtomicValue or a SingletonItem. In all other cases, the SequenceExtent will be returned unchanged.

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

Returns:

the value in simplified form

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

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

Overrides:

getItemType in class Value

Parameters:

th - the type hierarchy cache

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)

Specified by:

itemAt in interface GroundedValue

Overrides:

itemAt in class Value

Parameters:

n - the position of the required item

Returns:

the n'th item in the sequence

swap

public void swap(int a,
                 int b)

Swap two items (needed to support sorting)

Parameters:

a - the position of the first item to be swapped

b - the position of the second item to be swapped

iterate

public SequenceIterator iterate()

Return an iterator over this sequence.

Specified by:

iterate in class Value

Returns:

the required SequenceIterator, positioned at the start of the sequence

reverseIterate

public UnfailingIterator reverseIterate()

Return an enumeration of this sequence in reverse order (used for reverse axes)

Returns:

an AxisIterator that processes the items in reverse order

effectiveBooleanValue

public boolean effectiveBooleanValue()
                              throws XPathException

Get the effective boolean value

Overrides:

effectiveBooleanValue in class Value

Returns:

the effective boolean value

Throws:

XPathException - if any dynamic error occurs evaluating the expression

subsequence

public GroundedValue subsequence(int start,
                                 int length)

Get a subsequence of the value

Specified by:

subsequence in interface GroundedValue

Parameters:

start - the index of the first item to be included in the result, counting from zero. A negative value is taken as zero. If the value is beyond the end of the sequence, an empty sequence is returned

length - the number of items to be included in the result. Specify Integer.MAX_VALUE to get the subsequence up to the end of the base sequence. If the value is negative, an empty sequence is returned. If the value goes off the end of the sequence, the result returns items up to the end of the sequence

Returns:

the required subsequence. If min is

toString

public String toString()

Overrides:

toString in class Object