gamma.hpp

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/** \file gamma.hpp
 * \brief Declares and defines the gamma function.
 * \ingroup gen_math_files
 * \author Jared R. Males (jaredmales@gmail.com)
 *
 */
 
//***********************************************************************//
// Copyright 2020 Jared R. Males (jaredmales@gmail.com)
//
// This file is part of mxlib.
//
// mxlib is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// mxlib is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with mxlib.  If not, see <http://www.gnu.org/licenses/>.
//***********************************************************************//
 
#ifndef mx_gamma_hpp
#define mx_gamma_hpp
 
#include <type_traits>
 
#ifdef MX_INCLUDE_BOOST
#include <boost/math/special_functions/gamma.hpp>
#endif
 
namespace mx
{
namespace math
{
namespace func
{
 
/// The Gamma Function
/** This is a wrapper for boost.
 *
 * \tparam T a real floating point type
 *
 * \returns the value of the Gamma Function.
 *
 * \ingroup gen_math_gamma
 */
template <typename T>
T tgamma( T x /**< [in] the argument of the gamma function*/ )
{
#ifdef MX_INCLUDE_BOOST
    return boost::math::tgamma<T>( x );
#else
    static_assert(
        std::is_fundamental<T>::value || !std::is_fundamental<T>::value,
        "tgamma<T> not specialized for type T, and MX_INCLUDE_BOOST is not defined, so I can't just use boost." );
    return 0;
#endif
}
 
template <>
float tgamma<float>( float x );
 
template <>
double tgamma<double>( double x );
 
template <>
long double tgamma<long double>( long double x );
 
#ifdef HASQUAD
template <>
__float128 tgamma<__float128>( __float128 x );
#endif
 
} // namespace func
} // namespace math
} // namespace mx
 
#endif // mx_gamma_hpp