/*
 * 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.lang3.function;

import java.util.function.DoubleFunction;

/**
 * A functional interface like {@link DoubleFunction} that declares a
 * {@code Throwable}.
 *
 * @param <R> Return type.
 * @param <E> Thrown exception.
 * @since 3.11
 */
@FunctionalInterface
public interface FailableDoubleFunction<R, E extends Throwable> {

	/** NOP singleton */
	@SuppressWarnings("rawtypes")
	FailableDoubleFunction NOP = t -> null;

	/**
	 * Returns The NOP singleton.
	 *
	 * @param <R> Return type.
	 * @param <E> Thrown exception.
	 * @return The NOP singleton.
	 */
	static <R, E extends Throwable> FailableDoubleFunction<R, E> nop() {
		return NOP;
	}

	/**
	 * Applies this function.
	 *
	 * @param input the input for the function
	 * @return the result of the function
	 * @throws E Thrown when the function fails.
	 */
	R apply(double input) throws E;
}
