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.functor.core.composite;
018
019 import java.io.Serializable;
020
021 import org.apache.commons.functor.BinaryFunction;
022
023 /**
024 * A {@link BinaryFunction BinaryFunction} composed of
025 * three binary functions, <i>f</i>, <i>g</i> and <i>h</i>,
026 * evaluating the ordered parameters <i>x</i>, <i>y</i>
027 * to <code><i>f</i>(<i>g</i>(<i>x</i>,<i>y</i>),<i>h</i>(<i>x</i>,<i>y</i>))</code>.
028 * <p>
029 * Note that although this class implements
030 * {@link Serializable}, a given instance will
031 * only be truly <code>Serializable</code> if all the
032 * underlying functors are. Attempts to serialize
033 * an instance whose delegates are not all
034 * <code>Serializable</code> will result in an exception.
035 * </p>
036 * @version $Revision: 1171154 $ $Date: 2011-09-15 17:58:38 +0200 (Thu, 15 Sep 2011) $
037 * @author Rodney Waldhoff
038 */
039 public class BinaryCompositeBinaryFunction<L, R, T> implements BinaryFunction<L, R, T>, Serializable {
040
041 /**
042 * serialVersionUID declaration.
043 */
044 private static final long serialVersionUID = 2570517284319064043L;
045
046 /** Base hash integer used to shift hash */
047 private static final int HASH_SHIFT = 4;
048
049 /**
050 * Type-remembering Helper
051 *
052 * @param <G>
053 * @param <H>
054 */
055 private static class Helper<G, H, L, R, T> implements BinaryFunction<L, R, T>, Serializable {
056 /**
057 * serialVersionUID declaration.
058 */
059 private static final long serialVersionUID = 6013646799505641592L;
060 private BinaryFunction<? super G, ? super H, ? extends T> f;
061 private BinaryFunction<? super L, ? super R, ? extends G> g;
062 private BinaryFunction<? super L, ? super R, ? extends H> h;
063
064 /**
065 * Create a new Helper.
066 * @param f final BinaryFunction to evaluate
067 * @param g left preceding BinaryFunction
068 * @param h right preceding BinaryFunction
069 */
070 public Helper(BinaryFunction<? super G, ? super H, ? extends T> f,
071 BinaryFunction<? super L, ? super R, ? extends G> g,
072 BinaryFunction<? super L, ? super R, ? extends H> h) {
073 this.f = f;
074 this.g = g;
075 this.h = h;
076 }
077
078 /**
079 * {@inheritDoc}
080 */
081 public T evaluate(L left, R right) {
082 return f.evaluate(g.evaluate(left, right), h.evaluate(left, right));
083 }
084 }
085
086 private final Helper<?, ?, L, R, T> helper;
087
088 // constructor
089 // ------------------------------------------------------------------------
090 /**
091 * Create a new BinaryCompositeBinaryFunction.
092 * @param f final BinaryFunction to evaluate
093 * @param g left preceding BinaryFunction
094 * @param h right preceding BinaryFunction
095 */
096 public <G, H> BinaryCompositeBinaryFunction(BinaryFunction<? super G, ? super H, ? extends T> f,
097 BinaryFunction<? super L, ? super R, ? extends G> g, BinaryFunction<? super L, ? super R, ? extends H> h) {
098 if (f == null || g == null || h == null) {
099 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 }