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.composite;
18
19 import java.io.Serializable;
20
21 import org.apache.commons.functor.BinaryFunction;
22
23 /**
24 * A {@link BinaryFunction BinaryFunction} composed of
25 * three binary functions, <i>f</i>, <i>g</i> and <i>h</i>,
26 * evaluating the ordered parameters <i>x</i>, <i>y</i>
27 * to <code><i>f</i>(<i>g</i>(<i>x</i>,<i>y</i>),<i>h</i>(<i>x</i>,<i>y</i>))</code>.
28 * <p>
29 * Note that although this class implements
30 * {@link Serializable}, a given instance will
31 * only be truly <code>Serializable</code> if all the
32 * underlying functors are. Attempts to serialize
33 * an instance whose delegates are not all
34 * <code>Serializable</code> will result in an exception.
35 * </p>
36 * @version $Revision: 1171154 $ $Date: 2011-09-15 17:58:38 +0200 (Thu, 15 Sep 2011) $
37 * @author Rodney Waldhoff
38 */
39 public class BinaryCompositeBinaryFunction<L, R, T> implements BinaryFunction<L, R, T>, Serializable {
40
41 /**
42 * serialVersionUID declaration.
43 */
44 private static final long serialVersionUID = 2570517284319064043L;
45
46 /** Base hash integer used to shift hash */
47 private static final int HASH_SHIFT = 4;
48
49 /**
50 * Type-remembering Helper
51 *
52 * @param <G>
53 * @param <H>
54 */
55 private static class Helper<G, H, L, R, T> implements BinaryFunction<L, R, T>, Serializable {
56 /**
57 * serialVersionUID declaration.
58 */
59 private static final long serialVersionUID = 6013646799505641592L;
60 private BinaryFunction<? super G, ? super H, ? extends T> f;
61 private BinaryFunction<? super L, ? super R, ? extends G> g;
62 private BinaryFunction<? super L, ? super R, ? extends H> h;
63
64 /**
65 * Create a new Helper.
66 * @param f final BinaryFunction to evaluate
67 * @param g left preceding BinaryFunction
68 * @param h right preceding BinaryFunction
69 */
70 public Helper(BinaryFunction<? super G, ? super H, ? extends T> f,
71 BinaryFunction<? super L, ? super R, ? extends G> g,
72 BinaryFunction<? super L, ? super R, ? extends H> h) {
73 this.f = f;
74 this.g = g;
75 this.h = h;
76 }
77
78 /**
79 * {@inheritDoc}
80 */
81 public T evaluate(L left, R right) {
82 return f.evaluate(g.evaluate(left, right), h.evaluate(left, right));
83 }
84 }
85
86 private final Helper<?, ?, L, R, T> helper;
87
88 // constructor
89 // ------------------------------------------------------------------------
90 /**
91 * Create a new BinaryCompositeBinaryFunction.
92 * @param f final BinaryFunction to evaluate
93 * @param g left preceding BinaryFunction
94 * @param h right preceding BinaryFunction
95 */
96 public <G, H> BinaryCompositeBinaryFunction(BinaryFunction<? super G, ? super H, ? extends T> f,
97 BinaryFunction<? super L, ? super R, ? extends G> g, BinaryFunction<? super L, ? super R, ? extends H> h) {
98 if (f == null || g == null || h == null) {
99 throw new IllegalArgumentException("BinaryFunction arguments may not be null");
100 }
101 this.helper = new Helper<G, H, L, R, T>(f, g, h);
102 }
103
104 // function interface
105 // ------------------------------------------------------------------------
106 /**
107 * {@inheritDoc}
108 */
109 public final T evaluate(L left, R right) {
110 return helper.evaluate(left, right);
111 }
112
113 /**
114 * {@inheritDoc}
115 */
116 public final boolean equals(Object that) {
117 return that == this || (that instanceof BinaryCompositeBinaryFunction<?, ?, ?>
118 && equals((BinaryCompositeBinaryFunction<?, ?, ?>) that));
119 }
120
121 /**
122 * Learn whether another BinaryCompositeBinaryFunction is equal to this.
123 * @param that BinaryCompositeBinaryFunction to test
124 * @return boolean
125 */
126 public final boolean equals(BinaryCompositeBinaryFunction<?, ?, ?> that) {
127 return null != that
128 && helper.f.equals(that.helper.f)
129 && helper.g.equals(that.helper.g)
130 && helper.h.equals(that.helper.h);
131 }
132
133 /**
134 * {@inheritDoc}
135 */
136 public int hashCode() {
137 int hash = "BinaryCompositeBinaryFunction".hashCode();
138 hash <<= HASH_SHIFT;
139 hash ^= helper.f.hashCode();
140 hash <<= HASH_SHIFT;
141 hash ^= helper.g.hashCode();
142 hash <<= HASH_SHIFT;
143 hash ^= helper.h.hashCode();
144 return hash;
145 }
146
147 /**
148 * {@inheritDoc}
149 */
150 public String toString() {
151 return "BinaryCompositeBinaryFunction<" + helper.f + ";" + helper.g + ";" + helper.h + ">";
152 }
153
154 }