com.saxonica.expr
Class IndexedValue<T extends Item>

java.lang.Object
  net.sf.saxon.value.Value<T>
      com.saxonica.expr.IndexedValue<T>

All Implemented Interfaces:

ValueRepresentation<T>

public class IndexedValue<T extends Item>
extends Value<T>

A representation of a (sequence) value that allows the construction of one or more indexes to provide rapid access to the items in the sequence.

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

IndexedValue(SequenceIterator<T> iter)
Construct an indexed value (that is, a value that is capable of being indexed).

Method Summary

SequenceIterator<T>	findItems(Expression use, SequenceIterator values, boolean convertUntypedToOther, boolean firstOnly, AtomicComparer comparer, XPathContext context) Retrieve items that match a given index value
int	getLength() Get the length of the sequence
T	itemAt(int n) Get the n'th item in the sequence (starting from 0).
SequenceIterator<T>	iterate() Return an Iterator to iterate over the values of a sequence.

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

asItem, asItem, asIterator, asValue, checkPermittedContents, convertToJava, effectiveBooleanValue, equals, fromItem, getCanonicalLexicalRepresentation, getCardinality, getItemType, getIterator, getSchemaComparable, getSequenceLength, getStringValue, getStringValueCS, hashCode, isIdentical, process, reduce

Methods inherited from class java.lang.Object

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

Constructor Detail

IndexedValue

public IndexedValue(SequenceIterator<T> iter)
             throws XPathException

Construct an indexed value (that is, a value that is capable of being indexed). Initially there will be no indexes, these are added later.

Parameters:

iter - iterator over the items to be included in the indexed value

Throws:

XPathException - if an error occurs reading the iterator

Method Detail

iterate

public SequenceIterator<T> iterate()
                                         throws XPathException

Return an Iterator to iterate over the values of a sequence. The value of every expression can be regarded as a sequence, so this method is supported for all expressions. This default implementation handles iteration for expressions that return singleton values: for non-singleton expressions, the subclass must provide its own implementation.

Specified by:

iterate in class Value<T extends Item>

Returns:

a SequenceIterator that can be used to iterate over the result of the expression

Throws:

XPathException - if any dynamic error occurs evaluating the expression

itemAt

public T itemAt(int n)
                      throws XPathException

Get the n'th item in the sequence (starting from 0). This is defined for all Values, but its real benefits come for a sequence Value stored extensionally (or for a MemoClosure, once all the values have been read)

Overrides:

itemAt in class Value<T extends Item>

Parameters:

n - position of the required item, counting from zero.

Returns:

the n'th item in the sequence, where the first item in the sequence is numbered zero. If n is negative or >= the length of the sequence, returns null.

Throws:

XPathException - if an error occurs (for example if the value is a Closure that needs to be evaluated to find the Nth item)

getLength

public int getLength()
              throws XPathException

Get the length of the sequence

Overrides:

getLength in class Value<T extends Item>

Returns:

the number of items in the sequence

Throws:

XPathException - if an error occurs (for example if the value is a closure that needs to be read to determine its length)

findItems

public SequenceIterator<T> findItems(Expression use,
                                     SequenceIterator values,
                                     boolean convertUntypedToOther,
                                     boolean firstOnly,
                                     AtomicComparer comparer,
                                     XPathContext context)
                                           throws XPathException

Retrieve items that match a given index value

Parameters:

use - the expression whose value is to be matched

values - the set of values to be found

convertUntypedToOther - true if untypedAtomic values are to be converted to the type of the other operand

firstOnly - true if only the first matching item is required

comparer - AtomicComparer used to compare values for equality (encapsulates a collation if necessary)

context - the dynamic evaluation context @return an iterator over the items that match the specified values

Throws:

XPathException