/*
* File: EntryIndexComparator.java
* Authors: Justin Basilico
* Company: Sandia National Laboratories
* Project: Cognitive Framework Lite
*
* Copyright July 31, 2006, Sandia Corporation. Under the terms of Contract
* DE-AC04-94AL85000, there is a non-exclusive license for use of this work by
* or on behalf of the U.S. Government. Export of this program may require a
* license from the United States Government. See CopyrightHistory.txt for
* complete details.
*
*
*/
package gov.sandia.cognition.math.matrix;
/**
* The EntryIndexComparator interface defines the functionality of a comparator
* for index entries. It is not a standard Comparator because it handles null
* entries in a graceful manner by having the return type indicate which
* parameter is null.
*
* @param <EntryType> Entry that this Comparator function upon
* @author Justin Basilico
* @since 1.0
*/
public interface EntryIndexComparator<EntryType>
{
/**
* Indicates which of two iterators has the lowest index
*/
public enum Compare
{
/**
* first iterator has lowest index
*/
FIRST_LOWEST,
/**
* second iterator has lowest index
*/
SECOND_LOWEST,
/**
* both iterators are equally indexed
*/
ENTRIES_EQUAL,
/**
* both entries are null
*/
BOTH_ENTRIES_NULL,
/**
* first entry is null
*/
FIRST_ENTRY_NULL,
/**
* second entry is null
*/
SECOND_ENTRY_NULL
}
/**
* Determines which iterator has the lowest index
*
* @param firstEntry
* first entry to consider
* @param secondEntry
* second entry to consider
*
* @return FIRST_LOWEST if firstIterator has lowest index,
* SECOND_LOWEST if secondIterator has lowest index,
* ENTRIES_EQUAL if both are equal
* BOTH_ENTRIES_NULL if both are null
* FIRST_ENTRY_NULL if first entry is null
* SECOND_ENTRY_NULL if second entryis null
*/
public Compare lowestIndex(
EntryType firstEntry,
EntryType secondEntry );
}