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.statistics.distribution;
18
19 /**
20 * Constants for distribution calculations.
21 *
22 * <p>Constants should evaluate to the closest IEEE {@code double}.
23 * Expressions may have been computed using an arbitrary precision math
24 * library or obtained from existing online resources.
25 * Some expressions will not be the closest {@code double} if evaluated
26 * using the JDK's Math functions using {@code double} precision.
27 */
28 final class Constants {
29 /** sqrt(2). https://oeis.org/A002193. */
30 static final double ROOT_TWO = 1.4142135623730951;
31 /** sqrt(2 / pi). https://oeis.org/A076668. */
32 static final double ROOT_TWO_DIV_PI = 0.7978845608028654;
33 /** sqrt(pi / 2). https://oeis.org/A069998. */
34 static final double ROOT_PI_DIV_TWO = 1.2533141373155003;
35 /** ln(2). https://oeis.org/A002162. */
36 static final double LN_TWO = 0.6931471805599453;
37 /** 0.5 * ln(2 pi). https://oeis.org/A075700. */
38 static final double HALF_LOG_TWO_PI = 0.9189385332046728;
39
40 /** No instances. */
41 private Constants() {}
42 }