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.adapter;
18
19 import org.apache.commons.functor.BinaryFunction;
20 import org.apache.commons.functor.UnaryFunction;
21
22 /**
23 * Adapts a BinaryFunction as a UnaryFunction by sending the same argument to both sides of the BinaryFunction.
24 * It sounds nonsensical, but using Composite functions, can be made to do something useful.
25 * @param <A> the argument type.
26 * @param <T> the returned value type.
27 * @version $Revision: 1156765 $ $Date: 2011-08-11 21:37:08 +0200 (Thu, 11 Aug 2011) $
28 * @author Rodney Waldhoff
29 */
30 public final class BinaryFunctionUnaryFunction<A, T> implements UnaryFunction<A, T> {
31 /**
32 * The adapted function.
33 */
34 private final BinaryFunction<? super A, ? super A, ? extends T> function;
35
36 /**
37 * Create a new BinaryFunctionUnaryFunction.
38 * @param function to adapt
39 */
40 public BinaryFunctionUnaryFunction(BinaryFunction<? super A, ? super A, ? extends T> function) {
41 if (null == function) {
42 throw new IllegalArgumentException("BinaryFunction argument was null");
43 }
44 this.function = function;
45 }
46
47 /**
48 * {@inheritDoc}
49 */
50 public T evaluate(A obj) {
51 return function.evaluate(obj, obj);
52 }
53
54 /**
55 * {@inheritDoc}
56 */
57 @Override
58 public boolean equals(Object obj) {
59 return obj == this || obj instanceof BinaryFunctionUnaryFunction<?, ?>
60 && equals((BinaryFunctionUnaryFunction<?, ?>) obj);
61 }
62
63 /**
64 * Learn whether another BinaryFunctionUnaryFunction is equal to <code>this</code>.
65 * @param that BinaryFunctionUnaryFunction to check
66 * @return whether equal
67 */
68 public boolean equals(BinaryFunctionUnaryFunction<?, ?> that) {
69 return that != null && that.function.equals(this.function);
70 }
71
72 /**
73 * {@inheritDoc}
74 */
75 @Override
76 public int hashCode() {
77 return ("BinaryFunctionUnaryFunction".hashCode() << 2) | function.hashCode();
78 }
79
80 /**
81 * {@inheritDoc}
82 */
83 @Override
84 public String toString() {
85 return "BinaryFunctionUnaryFunction<" + function + ">";
86 }
87
88 /**
89 * Adapt a BinaryFunction as a UnaryFunction.
90 * @param <A> input type
91 * @param <T> result type
92 * @param function to adapt
93 * @return UnaryFunction<A, T>
94 */
95 public static <A, T> UnaryFunction<A, T> adapt(BinaryFunction<? super A, ? super A, ? extends T> function) {
96 return null == function ? null : new BinaryFunctionUnaryFunction<A, T>(function);
97 }
98
99 }