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pow.hpp
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pow.hpp
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/*################################################################################
##
## Copyright (C) 2016-2024 Keith O'Hara
##
## This file is part of the GCE-Math C++ library.
##
## Licensed 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.
##
################################################################################*/
/*
* compile-time power function
*/
#ifndef _gcem_pow_HPP
#define _gcem_pow_HPP
namespace internal
{
template<typename T>
constexpr
T
pow_dbl(const T base, const T exp_term)
noexcept
{
return exp(exp_term*log(base));
}
template<typename T1, typename T2, typename TC = common_t<T1,T2>,
typename std::enable_if<!std::is_integral<T2>::value>::type* = nullptr>
constexpr
TC
pow_check(const T1 base, const T2 exp_term)
noexcept
{
return( base < T1(0) ? \
GCLIM<TC>::quiet_NaN() :
//
pow_dbl(static_cast<TC>(base),static_cast<TC>(exp_term)) );
}
template<typename T1, typename T2, typename TC = common_t<T1,T2>,
typename std::enable_if<std::is_integral<T2>::value>::type* = nullptr>
constexpr
TC
pow_check(const T1 base, const T2 exp_term)
noexcept
{
return pow_integral(base,exp_term);
}
}
/**
* Compile-time power function
*
* @param base a real-valued input.
* @param exp_term a real-valued input.
* @return Computes \c base raised to the power \c exp_term. In the case where \c exp_term is integral-valued, recursion by squaring is used, otherwise \f$ \text{base}^{\text{exp\_term}} = e^{\text{exp\_term} \log(\text{base})} \f$
*/
template<typename T1, typename T2>
constexpr
common_t<T1,T2>
pow(const T1 base, const T2 exp_term)
noexcept
{
return internal::pow_check(base,exp_term);
}
#endif