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.math.linear;
019    
020    import org.apache.commons.math.linear.MatrixVisitorException;
021    
022    /**
023     * Interface defining a visitor for matrix entries.
024     *
025     * @see DefaultRealMatrixChangingVisitor
026     * @version $Revision: 1073158 $ $Date: 2011-02-21 22:46:52 +0100 (lun. 21 f??vr. 2011) $
027     * @since 2.0
028     */
029    public interface RealMatrixChangingVisitor {
030    
031        /**
032         * Start visiting a matrix.
033         * <p>This method is called once before any entry of the matrix is visited.</p>
034         * @param rows number of rows of the matrix
035         * @param columns number of columns of the matrix
036         * @param startRow Initial row index
037         * @param endRow Final row index (inclusive)
038         * @param startColumn Initial column index
039         * @param endColumn Final column index (inclusive)
040         */
041        void start(int rows, int columns,
042                   int startRow, int endRow, int startColumn, int endColumn);
043    
044        /**
045         * Visit one matrix entry.
046         * @param row row index of the entry
047         * @param column column index of the entry
048         * @param value current value of the entry
049         * @return the new value to be set for the entry
050         * @throws MatrixVisitorException if something wrong occurs
051         */
052        double visit(int row, int column, double value)
053            throws MatrixVisitorException;
054    
055        /**
056         * End visiting a matrix.
057         * <p>This method is called once after all entries of the matrix have been visited.</p>
058         * @return the value that the <code>walkInXxxOrder</code> must return
059         */
060        double end();
061    
062    }