org.apache.commons.statistics.distribution.Constants Maven / Gradle / Ivy
/*
* 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.statistics.distribution;
/**
* Constants for distribution calculations.
*
* Constants should evaluate to the closest IEEE {@code double}.
* Expressions may have been computed using an arbitrary precision math
* library or obtained from existing online resources.
* Some expressions will not be the closest {@code double} if evaluated
* using the JDK's Math functions using {@code double} precision.
*/
final class Constants {
/** sqrt(2). https://oeis.org/A002193. */
static final double ROOT_TWO = 1.4142135623730951;
/** sqrt(2 / pi). https://oeis.org/A076668. */
static final double ROOT_TWO_DIV_PI = 0.7978845608028654;
/** sqrt(pi / 2). https://oeis.org/A069998. */
static final double ROOT_PI_DIV_TWO = 1.2533141373155003;
/** ln(2). https://oeis.org/A002162. */
static final double LN_TWO = 0.6931471805599453;
/** 0.5 * ln(2 pi). https://oeis.org/A075700. */
static final double HALF_LOG_TWO_PI = 0.9189385332046728;
/** No instances. */
private Constants() {}
}