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
018package org.apache.commons.lang3.function;
019
020import java.util.Objects;
021import java.util.function.DoubleUnaryOperator;
022
023/**
024 * A functional interface like {@link DoubleUnaryOperator} that declares a {@code Throwable}.
025 *
026 * @param <E> Thrown exception.
027 * @since 3.11
028 */
029public interface FailableDoubleUnaryOperator<E extends Throwable> {
030
031    /** NOP singleton */
032    @SuppressWarnings("rawtypes")
033    FailableDoubleUnaryOperator NOP = t -> 0d;
034
035    /**
036     * Returns a unary operator that always returns its input argument.
037     *
038     * @param <E> Thrown exception.
039     * @return a unary operator that always returns its input argument
040     */
041    static <E extends Throwable> FailableDoubleUnaryOperator<E> identity() {
042        return t -> t;
043    }
044
045    /**
046     * Returns The NOP singleton.
047     *
048     * @param <E> Thrown exception.
049     * @return The NOP singleton.
050     */
051    static <E extends Throwable> FailableDoubleUnaryOperator<E> nop() {
052        return NOP;
053    }
054
055    /**
056     * Returns a composed {@code FailableDoubleUnaryOperator} like
057     * {@link DoubleUnaryOperator#andThen(DoubleUnaryOperator)}.
058     *
059     * @param after the operator to apply after this one.
060     * @return a composed {@code FailableDoubleUnaryOperator} like
061     *         {@link DoubleUnaryOperator#andThen(DoubleUnaryOperator)}.
062     * @throws NullPointerException if after is null.
063     * @see #compose(FailableDoubleUnaryOperator)
064     */
065    default FailableDoubleUnaryOperator<E> andThen(final FailableDoubleUnaryOperator<E> after) {
066        Objects.requireNonNull(after);
067        return (final double t) -> after.applyAsDouble(applyAsDouble(t));
068    }
069
070    /**
071     * Applies this operator to the given operand.
072     *
073     * @param operand the operand
074     * @return the operator result
075     * @throws E Thrown when a consumer fails.
076     */
077    double applyAsDouble(double operand) throws E;
078
079    /**
080     * Returns a composed {@code FailableDoubleUnaryOperator} like
081     * {@link DoubleUnaryOperator#compose(DoubleUnaryOperator)}.
082     *
083     * @param before the operator to apply before this one.
084     * @return a composed {@code FailableDoubleUnaryOperator} like
085     *         {@link DoubleUnaryOperator#compose(DoubleUnaryOperator)}.
086     * @throws NullPointerException if before is null.
087     * @see #andThen(FailableDoubleUnaryOperator)
088     */
089    default FailableDoubleUnaryOperator<E> compose(final FailableDoubleUnaryOperator<E> before) {
090        Objects.requireNonNull(before);
091        return (final double v) -> applyAsDouble(before.applyAsDouble(v));
092    }
093}