| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.commons.functor.core.composite; |
| |
| import java.io.Serializable; |
| |
| import org.apache.commons.functor.BinaryFunction; |
| import org.apache.commons.lang3.Validate; |
| |
| /** |
| * Transposes (swaps) the arguments to some other |
| * {@link BinaryFunction function}. |
| * For example, given a function <i>f</i> |
| * and the ordered pair of arguments <i>a</i>, |
| * <i>b</i>. |
| * {@link #evaluate evaluates} to |
| * <code>f.evaluate(b,a)</code>. |
| * <p> |
| * Note that although this class implements |
| * {@link Serializable}, a given instance will |
| * only be truly <code>Serializable</code> if the |
| * underlying functor is. Attempts to serialize |
| * an instance whose delegate is not |
| * <code>Serializable</code> will result in an exception. |
| * </p> |
| * |
| * @param <L> the left argument type. |
| * @param <R> the right argument type. |
| * @param <T> the returned value type. |
| * @version $Revision$ $Date$ |
| */ |
| public class TransposedFunction<L, R, T> implements BinaryFunction<L, R, T>, Serializable { |
| /** |
| * serialVersionUID declaration. |
| */ |
| private static final long serialVersionUID = -5824252875453493940L; |
| // attributes |
| // ------------------------------------------------------------------------ |
| /** |
| * The adapted function. |
| */ |
| private final BinaryFunction<? super R, ? super L, ? extends T> function; |
| |
| // constructor |
| // ------------------------------------------------------------------------ |
| /** |
| * Create a new TransposedFunction. |
| * @param function BinaryFunction to transpose. |
| */ |
| public TransposedFunction(BinaryFunction<? super R, ? super L, ? extends T> function) { |
| this.function = Validate.notNull(function, "BinaryFunction argument was null"); |
| } |
| |
| // functor interface |
| // ------------------------------------------------------------------------ |
| /** |
| * {@inheritDoc} |
| */ |
| public final T evaluate(L left, R right) { |
| return function.evaluate(right, left); |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public final boolean equals(Object that) { |
| return that == this || (that instanceof TransposedFunction<?, ?, ?> |
| && equals((TransposedFunction<?, ?, ?>) that)); |
| } |
| |
| /** |
| * Learn whether another TransposedFunction is equal to this. |
| * @param that TransposedFunction to test |
| * @return boolean |
| */ |
| public final boolean equals(TransposedFunction<?, ?, ?> that) { |
| return null != that && function.equals(that.function); |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public int hashCode() { |
| int hash = "TransposedFunction".hashCode(); |
| hash ^= function.hashCode(); |
| return hash; |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public String toString() { |
| return "TransposedFunction<" + function + ">"; |
| } |
| |
| // static |
| // ------------------------------------------------------------------------ |
| /** |
| * Transpose a BinaryFunction. |
| * @param <L> the left argument type. |
| * @param <R> the right argument type. |
| * @param <T> the returned value type. |
| * @param f BinaryFunction to transpose |
| * @return TransposedFunction |
| */ |
| public static <L, R, T> TransposedFunction<R, L, T> transpose(BinaryFunction<? super L, ? super R, ? extends T> f) { |
| return null == f ? null : new TransposedFunction<R, L, T>(f); |
| } |
| |
| } |