    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 {@link Throwable}.
    025 *
    026 * @param <E> The kind of thrown exception or error.
    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> The kind of thrown exception or error.
    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> The kind of thrown exception or error.
    049     * @return The NOP singleton.
    050     */
    051    @SuppressWarnings("unchecked")
    052    static <E extends Throwable> FailableDoubleUnaryOperator<E> nop() {
    053        return NOP;
    054    }
    055
    056    /**
    057     * Returns a composed {@link FailableDoubleUnaryOperator} like
    058     * {@link DoubleUnaryOperator#andThen(DoubleUnaryOperator)}.
    059     *
    060     * @param after the operator to apply after this one.
    061     * @return a composed {@link FailableDoubleUnaryOperator} like
    062     *         {@link DoubleUnaryOperator#andThen(DoubleUnaryOperator)}.
    063     * @throws NullPointerException if after is null.
    064     * @see #compose(FailableDoubleUnaryOperator)
    065     */
    066    default FailableDoubleUnaryOperator<E> andThen(final FailableDoubleUnaryOperator<E> after) {
    067        Objects.requireNonNull(after);
    068        return (final double t) -> after.applyAsDouble(applyAsDouble(t));
    069    }
    070
    071    /**
    072     * Applies this operator to the given operand.
    073     *
    074     * @param operand the operand
    075     * @return the operator result
    076     * @throws E Thrown when a consumer fails.
    077     */
    078    double applyAsDouble(double operand) throws E;
    079
    080    /**
    081     * Returns a composed {@link FailableDoubleUnaryOperator} like
    082     * {@link DoubleUnaryOperator#compose(DoubleUnaryOperator)}.
    083     *
    084     * @param before the operator to apply before this one.
    085     * @return a composed {@link FailableDoubleUnaryOperator} like
    086     *         {@link DoubleUnaryOperator#compose(DoubleUnaryOperator)}.
    087     * @throws NullPointerException if before is null.
    088     * @see #andThen(FailableDoubleUnaryOperator)
    089     */
    090    default FailableDoubleUnaryOperator<E> compose(final FailableDoubleUnaryOperator<E> before) {
    091        Objects.requireNonNull(before);
    092        return (final double v) -> applyAsDouble(before.applyAsDouble(v));
    093    }
    094}