001/*
002 * Copyright (c) 2015-2020, Oracle and/or its affiliates. All rights reserved.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *     http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.tribuo.math.la;
018
019import java.util.Iterator;
020
021/**
022 * A {@link Comparable} {@link Iterator} over {@link MatrixTuple}s.
023 * <p>
024 * The comparison is based on the indices, not on the values.
025 * To use the comparator .next must have been called once.
026 */
027public interface MatrixIterator extends Iterator<MatrixTuple>, Comparable<MatrixIterator> {
028
029    /**
030     * Gets the MatrixTuple reference that this iterator updates.
031     * @return The matrix tuple.
032     */
033    public MatrixTuple getReference();
034
035    @Override
036    public default int compareTo(MatrixIterator o) {
037        MatrixTuple ours = getReference();
038        MatrixTuple other = o.getReference();
039        if (other.i < ours.i) {
040            return 1;
041        } else if (other.i > ours.i) {
042            return -1;
043        } else {
044            //other.i == pair.i;
045            return Integer.compare(ours.j, other.j);
046        }
047    }
048
049}