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 package org.apache.commons.functor.core;
18
19 import org.apache.commons.functor.BinaryFunction;
20 import org.apache.commons.functor.BinaryPredicate;
21 import org.apache.commons.functor.adapter.BinaryFunctionBinaryPredicate;
22 import org.apache.commons.functor.adapter.IgnoreLeftFunction;
23
24 /**
25 * Holder class for a right-identity <code>BinaryFunction</code> (evaluates to the right argument) and a right-identity
26 * <code>BinaryPredicate</code> (tests whether right <code>Boolean</code> argument equals <code>Boolean.TRUE</code>).
27 *
28 * @version $Revision: 1160415 $ $Date: 2011-08-22 22:14:38 +0200 (Mon, 22 Aug 2011) $
29 * @author Rodney Waldhoff
30 * @author Matt Benson
31 */
32 public final class RightIdentity {
33
34 // static attributes
35 // ------------------------------------------------------------------------
36 /**
37 * Right-identity function.
38 */
39 public static final BinaryFunction<Object, Object, Object> FUNCTION = RightIdentity.<Object, Object>function();
40
41 /**
42 * Right-identity predicate.
43 */
44 public static final BinaryPredicate<Object, Boolean> PREDICATE =
45 BinaryFunctionBinaryPredicate.adapt(IgnoreLeftFunction.adapt(new Identity<Boolean>()));
46
47 // constructor
48 // ------------------------------------------------------------------------
49 /**
50 * Create a new RightIdentity.
51 */
52 public RightIdentity() {
53 }
54
55 // static methods
56 // ------------------------------------------------------------------------
57
58 /**
59 * Get a typed right-identity BinaryFunction.
60 * @param <L> the left argument type.
61 * @param <R> the right argument type.
62 * @return BinaryFunction<L, R, R>
63 */
64 public static <L, R> BinaryFunction<L, R, R> function() {
65 return IgnoreLeftFunction.adapt(new Identity<R>());
66 }
67
68 /**
69 * Get a typed right-identity BinaryPredicate.
70 * @param <L> the left argument type.
71 * @return BinaryPredicate<L, Boolean>
72 */
73 public static <L> BinaryPredicate<L, Boolean> predicate() {
74 return BinaryFunctionBinaryPredicate.adapt(
75 IgnoreLeftFunction.<L, Boolean, Boolean>adapt(new Identity<Boolean>()));
76 }
77 }