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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.rng.sampling.distribution;
18  
19  import java.util.stream.DoubleStream;
20  
21  /**
22   * Sampler that generates values of type {@code double}.
23   *
24   * @since 1.0
25   */
26  public interface ContinuousSampler {
27      /**
28       * Creates a {@code double} sample.
29       *
30       * @return a sample.
31       */
32      double sample();
33  
34      /**
35       * Returns an effectively unlimited stream of {@code double} sample values.
36       *
37       * <p>The default implementation produces a sequential stream that repeatedly
38       * calls {@link #sample sample}().
39       *
40       * @return a stream of {@code double} values.
41       * @since 1.5
42       */
43      default DoubleStream samples() {
44          return DoubleStream.generate(this::sample).sequential();
45      }
46  
47      /**
48       * Returns a stream producing the given {@code streamSize} number of {@code double}
49       * sample values.
50       *
51       * <p>The default implementation produces a sequential stream that repeatedly
52       * calls {@link #sample sample}(); the stream is limited to the given {@code streamSize}.
53       *
54       * @param streamSize Number of values to generate.
55       * @return a stream of {@code double} values.
56       * @since 1.5
57       */
58      default DoubleStream samples(long streamSize) {
59          return samples().limit(streamSize);
60      }
61  }