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    package org.apache.commons.math3.linear;
018    
019    /**
020     * This interface defines a visitor for the entries of a vector. Visitors
021     * implementing this interface may alter the entries of the vector being
022     * visited.
023     *
024     * @version $Id: RealVectorChangingVisitor.java 1416643 2012-12-03 19:37:14Z tn $
025     * @since 3.1
026     */
027    public interface RealVectorChangingVisitor {
028        /**
029         * Start visiting a vector. This method is called once, before any entry
030         * of the vector is visited.
031         *
032         * @param dimension the size of the vector
033         * @param start the index of the first entry to be visited
034         * @param end the index of the last entry to be visited (inclusive)
035         */
036        void start(int dimension, int start, int end);
037    
038        /**
039         * Visit one entry of the vector.
040         *
041         * @param index the index of the entry being visited
042         * @param value the value of the entry being visited
043         * @return the new value of the entry being visited
044         */
045        double visit(int index, double value);
046    
047        /**
048         * End visiting a vector. This method is called once, after all entries of
049         * the vector have been visited.
050         *
051         * @return the value returned by
052         * {@link RealVector#walkInDefaultOrder(RealVectorChangingVisitor)},
053         * {@link RealVector#walkInDefaultOrder(RealVectorChangingVisitor, int, int)},
054         * {@link RealVector#walkInOptimizedOrder(RealVectorChangingVisitor)}
055         * or
056         * {@link RealVector#walkInOptimizedOrder(RealVectorChangingVisitor, int, int)}
057         */
058        double end();
059    }