public class IntervalIterators extends ObjectA class providing static methods and objects that do useful things with interval iterators.
public static final IntervalIterator TRUEA singleton iterator representing maximum truth.
This iterator is a placeholder for an iterator returning just
Intervals.EMPTY_INTERVAL. The antichain formed by the empty interval is the top element of the lattice of antichains, and thus represents the highest truth. Since, however,
EMPTY_INTERVALis a singleton that slightly violates the
Intervalinvariants, an iterator actually returning
EMPTY_INTERVALwould cause severe problems in all algorithms manipulating intervals. Rather,
TRUEis treated separately and is never actually used in an algorithm on interval antichains (also because, albeit it claims to have elements, it will return
Warning: Before 4.0, an
IndexIteratorby convention would have returned
DocumentIterator.intervalIterator(it.unimi.di.big.mg4j.index.Index)was called with an argument that was not the key index. Now it returns
public static final IntervalIterator FALSEA singleton empty interval iterator.
The main usefulness of this iterator is as a singleton: in some circumstances you have to return an empty iterator, and since it is by definition stateless, it is a pity to create a new object (the same considerations led to
This iterator is used by document iterators as a placeholder whenever
DocumentIterator.intervalIterator(it.unimi.di.big.mg4j.index.Index)is called on an index for which there are not intervals. For instance, an
IndexIteratorby convention returns
DocumentIterator.intervalIterator(it.unimi.di.big.mg4j.index.Index)is called with an argument that is not the key index. Before 4.0, the same placeholder role was held by
public static ObjectSet<Interval> pour(IntervalIterator intervalIterator) throws IOExceptionReturns a set containing the intervals enumerated by the specified interval iterators: iteration on the set is guarantee to return the intervals in the same order in which they were enumerated.
intervalIterator- an interval iterator.
- a set containing the intervals enumerated by