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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.commons.math.linear;
19  
20  import org.apache.commons.math.FieldElement;
21  
22  /**
23   * Default implementation of the {@link FieldMatrixChangingVisitor} interface.
24   * <p>
25   * This class is a convenience to create custom visitors without defining all
26   * methods. This class provides default implementations that do nothing.
27   * </p>
28   * 
29   * @param <T> the type of the field elements
30   * @version $Revision: 778191 $ $Date: 2009-05-24 12:44:52 -0400 (Sun, 24 May 2009) $
31   * @since 2.0
32   */
33  public class DefaultFieldMatrixChangingVisitor<T extends FieldElement<T>>
34      implements FieldMatrixChangingVisitor<T> {
35  
36      /** Zero element of the field. */
37      private final T zero;
38  
39      /** Build a new instance.
40       * @param zero additive identity of the field
41       */
42      public DefaultFieldMatrixChangingVisitor(final T zero) {
43          this.zero = zero;
44      }
45  
46      /** {@inheritDoc} */
47      public void start(int rows, int columns,
48                        int startRow, int endRow, int startColumn, int endColumn) {
49      }
50  
51      /** {@inheritDoc} */
52      public T visit(int row, int column, T value)
53          throws MatrixVisitorException {
54          return value;
55      }
56  
57      /** {@inheritDoc} */
58      public T end() {
59          return zero;
60      }
61  
62  }