net.sf.saxon.expr

Class ReverseRangeIterator

java.lang.Object

net.sf.saxon.expr.ReverseRangeIterator

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, LastPositionFinder, SequenceIterator<AtomicValue>, AtomicIterator, LookaheadIterator<AtomicValue>, ReversibleIterator<AtomicValue>, UnfailingIterator<AtomicValue>

public class ReverseRangeIterator
extends java.lang.Object
implements AtomicIterator, ReversibleIterator<AtomicValue>, LastPositionFinder, LookaheadIterator<AtomicValue>

Iterator that produces numeric values in a monotonic sequence, ascending or descending. Although a range expression (N to M) is always in ascending order, applying the reverse() function will produce a RangeIterator that works in descending order.

Field Summary

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

ATOMIZING, GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

Constructor Summary

Constructors

Constructor and Description
ReverseRangeIterator(long start, long end) Create an iterator over a range of integers in monotonic descending order

Method Summary

Modifier and Type	Method and Description
int	getLength() Get the last position (that is, the number of items in the sequence).
int	getProperties() Get properties of this iterator, as a bit-significant integer.
AtomicIterator	getReverseIterator() Get a new SequenceIterator that returns the same items in reverse order.
boolean	hasNext() Determine whether there are more items to come.
IntegerValue	next() Get the next atomic value in the sequence.

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.sf.saxon.tree.iter.UnfailingIterator

firstWith, forEach, toGroundedValue, toList

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

close, forEachOrFail, materialize

Constructor Detail

ReverseRangeIterator

public ReverseRangeIterator(long start,
                            long end)
                     throws XPathException

Create an iterator over a range of integers in monotonic descending order

Parameters:

start - the first integer to be delivered (the highest in the range)

end - the last integer to be delivered (the lowest in the range). Must be <= start

Throws:

XPathException - if the values are inconsistent or if the length is greater than 2^31

Method Detail

hasNext

public boolean hasNext()

Description copied from interface: LookaheadIterator

Determine whether there are more items to come. Note that this operation is stateless and it is not necessary (or usual) to call it before calling next(). It is used only when there is an explicit need to tell if we are at the last element.

This method must not be called unless the result of getProperties() on the iterator includes the bit setting SequenceIterator.LOOKAHEAD

Specified by:

hasNext in interface LookaheadIterator<AtomicValue>

Returns:

true if there are more items in the sequence

next

public IntegerValue next()

Description copied from interface: AtomicIterator

Get the next atomic value in the sequence.

Specified by:

next in interface SequenceIterator<AtomicValue>

Specified by:

next in interface AtomicIterator

Specified by:

next in interface UnfailingIterator<AtomicValue>

Returns:

the next Item. If there are no more items, return null.

getLength

public int getLength()

Description copied from interface: LastPositionFinder

Get the last position (that is, the number of items in the sequence). This method is non-destructive: it does not change the state of the iterator. The result is undefined if the next() method of the iterator has already returned null. This method must not be called unless the result of getProperties() on the iterator includes the bit setting SequenceIterator.LAST_POSITION_FINDER

Specified by:

getLength in interface LastPositionFinder

Returns:

the number of items in the sequence

getProperties

public int getProperties()

Get properties of this iterator, as a bit-significant integer.

Specified by:

getProperties in interface SequenceIterator<AtomicValue>

Returns:

the properties of this iterator. This will be some combination of properties such as SequenceIterator.GROUNDED, SequenceIterator.LAST_POSITION_FINDER, and SequenceIterator.LOOKAHEAD. It is always acceptable to return the value zero, indicating that there are no known special properties. It is acceptable for the properties of the iterator to change depending on its state.

getReverseIterator

public AtomicIterator getReverseIterator()

Description copied from interface: ReversibleIterator

Get a new SequenceIterator that returns the same items in reverse order. If this SequenceIterator is an AxisIterator, then the returned SequenceIterator must also be an AxisIterator.

Specified by:

getReverseIterator in interface ReversibleIterator<AtomicValue>

Returns:

an iterator over the items in reverse order