    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
    018    package org.apache.commons.math3.linear;
    019
    020    /**
    021     * Interface defining a visitor for matrix entries.
    022     *
    023     * @see DefaultRealMatrixChangingVisitor
    024     * @version $Id: RealMatrixChangingVisitor.java 1416643 2012-12-03 19:37:14Z tn $
    025     * @since 2.0
    026     */
    027    public interface RealMatrixChangingVisitor {
    028        /**
    029         * Start visiting a matrix.
    030         * <p>This method is called once before any entry of the matrix is visited.</p>
    031         * @param rows number of rows of the matrix
    032         * @param columns number of columns of the matrix
    033         * @param startRow Initial row index
    034         * @param endRow Final row index (inclusive)
    035         * @param startColumn Initial column index
    036         * @param endColumn Final column index (inclusive)
    037         */
    038        void start(int rows, int columns,
    039                   int startRow, int endRow, int startColumn, int endColumn);
    040
    041        /**
    042         * Visit one matrix entry.
    043         * @param row row index of the entry
    044         * @param column column index of the entry
    045         * @param value current value of the entry
    046         * @return the new value to be set for the entry
    047         */
    048        double visit(int row, int column, double value);
    049
    050        /**
    051         * End visiting a matrix.
    052         * <p>This method is called once after all entries of the matrix have been visited.</p>
    053         * @return the value that the <code>walkInXxxOrder</code> must return
    054         */
    055        double end();
    056    }