WPILibC++ 2024.3.2
lbeta.hpp
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1/*################################################################################
2 ##
3 ## Copyright (C) 2016-2023 Keith O'Hara
4 ##
5 ## This file is part of the GCE-Math C++ library.
6 ##
8 ## you may not use this file except in compliance with the License.
9 ## You may obtain a copy of the License at
10 ##
12 ##
13 ## Unless required by applicable law or agreed to in writing, software
15 ## WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 ## See the License for the specific language governing permissions and
17 ## limitations under the License.
18 ##
19 ################################################################################*/
20
21#ifndef _gcem_lbeta_HPP
22#define _gcem_lbeta_HPP
23
24namespace gcem
25{
26
27/**
28 * Compile-time log-beta function
29 *
30 * @param a a real-valued input.
31 * @param b a real-valued input.
32 * @return the log-beta function using \f[ \ln \text{B}(\alpha,\beta) := \ln \int_0^1 t^{\alpha - 1} (1-t)^{\beta - 1} dt = \ln \Gamma(\alpha) + \ln \Gamma(\beta) - \ln \Gamma(\alpha + \beta) \f]
33 * where \f$\Gamma \f$ denotes the gamma function.
34 */
35
36template<typename T1, typename T2>
37constexpr
38common_return_t<T1,T2>
39lbeta(const T1 a, const T2 b)
40noexcept
41{
42 return( (lgamma(a) + lgamma(b)) - lgamma(a+b) );
43}
44
45}
46
47#endif
Definition: is_even.hpp:29
constexpr return_t< T > lgamma(const T x) noexcept
Compile-time log-gamma function.
Definition: lgamma.hpp:135
constexpr common_return_t< T1, T2 > lbeta(const T1 a, const T2 b) noexcept
Compile-time log-beta function.
Definition: lbeta.hpp:39
b
Definition: data.h:44