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.rng.sampling.distribution;
018
019import java.util.stream.DoubleStream;
020
021/**
022 * Sampler that generates values of type {@code double}.
023 *
024 * @since 1.0
025 */
026public interface ContinuousSampler {
027    /**
028     * Creates a {@code double} sample.
029     *
030     * @return a sample.
031     */
032    double sample();
033
034    /**
035     * Returns an effectively unlimited stream of {@code double} sample values.
036     *
037     * <p>The default implementation produces a sequential stream that repeatedly
038     * calls {@link #sample sample}().
039     *
040     * @return a stream of {@code double} values.
041     * @since 1.5
042     */
043    default DoubleStream samples() {
044        return DoubleStream.generate(this::sample).sequential();
045    }
046
047    /**
048     * Returns a stream producing the given {@code streamSize} number of {@code double}
049     * sample values.
050     *
051     * <p>The default implementation produces a sequential stream that repeatedly
052     * calls {@link #sample sample}(); the stream is limited to the given {@code streamSize}.
053     *
054     * @param streamSize Number of values to generate.
055     * @return a stream of {@code double} values.
056     * @since 1.5
057     */
058    default DoubleStream samples(long streamSize) {
059        return samples().limit(streamSize);
060    }
061}