001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.math4.linear;
019
020import org.apache.commons.math4.FieldElement;
021
022/**
023 * Interface defining a visitor for matrix entries.
024 *
025 * @param <T> the type of the field elements
026 * @since 2.0
027 */
028public interface FieldMatrixChangingVisitor<T extends FieldElement<?>> {
029    /**
030     * Start visiting a matrix.
031     * <p>This method is called once before any entry of the matrix is visited.</p>
032     * @param rows number of rows of the matrix
033     * @param columns number of columns of the matrix
034     * @param startRow Initial row index
035     * @param endRow Final row index (inclusive)
036     * @param startColumn Initial column index
037     * @param endColumn Final column index (inclusive)
038     */
039    void start(int rows, int columns,
040               int startRow, int endRow, int startColumn, int endColumn);
041
042    /**
043     * Visit one matrix entry.
044     * @param row row index of the entry
045     * @param column column index of the entry
046     * @param value current value of the entry
047     * @return the new value to be set for the entry
048     */
049    T visit(int row, int column, T value);
050
051    /**
052     * End visiting a matrix.
053     * <p>This method is called once after all entries of the matrix have been visited.</p>
054     * @return the value that the <code>walkInXxxOrder</code> must return
055     */
056    T end();
057}