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 */
017package org.apache.commons.functor.core.composite;
018
019import java.io.Serializable;
020
021import org.apache.commons.functor.BinaryFunction;
022import org.apache.commons.lang3.Validate;
023
024/**
025 * A {@link BinaryFunction BinaryFunction} composed of
026 * three binary functions, <i>f</i>, <i>g</i> and <i>h</i>,
027 * evaluating the ordered parameters <i>x</i>, <i>y</i>
028 * to <code><i>f</i>(<i>g</i>(<i>x</i>,<i>y</i>),<i>h</i>(<i>x</i>,<i>y</i>))</code>.
029 * <p>
030 * Note that although this class implements
031 * {@link Serializable}, a given instance will
032 * only be truly <code>Serializable</code> if all the
033 * underlying functors are.  Attempts to serialize
034 * an instance whose delegates are not all
035 * <code>Serializable</code> will result in an exception.
036 * </p>
037 * @param <L> the function left argument type.
038 * @param <R> the function right argument type.
039 * @param <T> the function returned value type.
040 * @version $Revision: 1345136 $ $Date: 2012-06-01 08:47:06 -0400 (Fri, 01 Jun 2012) $
041 */
042public class BinaryCompositeBinaryFunction<L, R, T> implements BinaryFunction<L, R, T>, Serializable {
043
044    /**
045     * serialVersionUID declaration.
046     */
047    private static final long serialVersionUID = 2570517284319064043L;
048
049    /** Base hash integer used to shift hash. */
050    private static final int HASH_SHIFT = 4;
051
052    /**
053     * Type-remembering Helper.
054     *
055     * @param <G> the function left argument type.
056     * @param <H> the function right argument type.
057     */
058    private static class Helper<G, H, L, R, T> implements BinaryFunction<L, R, T>, Serializable {
059        /**
060         * serialVersionUID declaration.
061         */
062        private static final long serialVersionUID = 6013646799505641592L;
063        /**
064         * Global evaluator.
065         */
066        private BinaryFunction<? super G, ? super H, ? extends T> f;
067        /**
068         * This function evaluation will be the left argument of main evaluator.
069         */
070        private BinaryFunction<? super L, ? super R, ? extends G> g;
071        /**
072         * This function evaluation will be the right argument of main evaluator.
073         */
074        private BinaryFunction<? super L, ? super R, ? extends H> h;
075
076        /**
077         * Create a new Helper.
078         * @param f final BinaryFunction to evaluate
079         * @param g left preceding BinaryFunction
080         * @param h right preceding BinaryFunction
081         */
082        public Helper(BinaryFunction<? super G, ? super H, ? extends T> f,
083                BinaryFunction<? super L, ? super R, ? extends G> g,
084                BinaryFunction<? super L, ? super R, ? extends H> h) {
085            this.f = f;
086            this.g = g;
087            this.h = h;
088        }
089
090        /**
091         * {@inheritDoc}
092         */
093        public T evaluate(L left, R right) {
094            return f.evaluate(g.evaluate(left, right), h.evaluate(left, right));
095        }
096    }
097
098    /**
099     * The helper used for the evaluation.
100     */
101    private final Helper<?, ?, L, R, T> helper;
102
103    // constructor
104    // ------------------------------------------------------------------------
105    /**
106     * Create a new BinaryCompositeBinaryFunction.
107     *
108     * @param <G> the main function left argument type.
109     * @param <H> the main function right argument type.
110     * @param f final BinaryFunction to evaluate
111     * @param g left preceding BinaryFunction
112     * @param h right preceding BinaryFunction
113     */
114    public <G, H> BinaryCompositeBinaryFunction(BinaryFunction<? super G, ? super H, ? extends T> f,
115            BinaryFunction<? super L, ? super R, ? extends G> g, BinaryFunction<? super L, ? super R, ? extends H> h) {
116        this.helper = new Helper<G, H, L, R, T>(
117                Validate.notNull(f, "final BinaryFunction argument must not be null"),
118                Validate.notNull(g, "left preceding BinaryFunction argument must not be null"),
119                Validate.notNull(h, "right preceding BinaryFunction argument must not be null")
120        );
121    }
122
123    // function interface
124    // ------------------------------------------------------------------------
125    /**
126     * {@inheritDoc}
127     */
128    public final T evaluate(L left, R right) {
129        return helper.evaluate(left, right);
130    }
131
132    /**
133     * {@inheritDoc}
134     */
135    @Override
136    public final boolean equals(Object that) {
137        return that == this || (that instanceof BinaryCompositeBinaryFunction<?, ?, ?>
138                                    && equals((BinaryCompositeBinaryFunction<?, ?, ?>) that));
139    }
140
141    /**
142     * Learn whether another BinaryCompositeBinaryFunction is equal to this.
143     * @param that BinaryCompositeBinaryFunction to test
144     * @return boolean
145     */
146    public final boolean equals(BinaryCompositeBinaryFunction<?, ?, ?> that) {
147        return null != that
148                && helper.f.equals(that.helper.f)
149                && helper.g.equals(that.helper.g)
150                && helper.h.equals(that.helper.h);
151    }
152
153    /**
154     * {@inheritDoc}
155     */
156    @Override
157    public int hashCode() {
158        int hash = "BinaryCompositeBinaryFunction".hashCode();
159            hash <<= HASH_SHIFT;
160            hash ^= helper.f.hashCode();
161            hash <<= HASH_SHIFT;
162            hash ^= helper.g.hashCode();
163            hash <<= HASH_SHIFT;
164            hash ^= helper.h.hashCode();
165        return hash;
166    }
167
168    /**
169     * {@inheritDoc}
170     */
171    @Override
172    public String toString() {
173        return "BinaryCompositeBinaryFunction<" + helper.f + ";" + helper.g + ";" + helper.h + ">";
174    }
175
176}