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    /**
021     * Interface defining a visitor for matrix entries.
022     * 
023     * @see DefaultRealMatrixPreservingVisitor
024     * @version $Revision: 778191 $ $Date: 2009-05-24 12:44:52 -0400 (Sun, 24 May 2009) $
025     * @since 2.0
026     */
027    public interface RealMatrixPreservingVisitor {
028    
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         * @throws MatrixVisitorException if something wrong occurs
048         */
049        void visit(int row, int column, double value)
050            throws MatrixVisitorException;
051    
052        /**
053         * End visiting a matrix.
054         * <p>This method is called once after all entries of the matrix have been visited.</p>
055         * @return the value that the <code>walkInXxxOrder</code> must return
056         */
057        double end();
058    
059    }