mirror of
https://github.com/bolero-MURAKAMI/Sprout.git
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90 lines
3 KiB
C++
90 lines
3 KiB
C++
/*=============================================================================
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Copyright (c) 2011-2019 Bolero MURAKAMI
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https://github.com/bolero-MURAKAMI/Sprout
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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=============================================================================*/
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#ifndef SPROUT_MATH_EXP_HPP
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#define SPROUT_MATH_EXP_HPP
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#include <type_traits>
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#include <sprout/config.hpp>
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#include <sprout/workaround/std/cstddef.hpp>
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#include <sprout/limits.hpp>
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#include <sprout/detail/pow.hpp>
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#include <sprout/math/detail/config.hpp>
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#include <sprout/math/detail/float_compute.hpp>
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#include <sprout/math/isnan.hpp>
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#include <sprout/math/factorial.hpp>
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#include <sprout/type_traits/enabler_if.hpp>
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namespace sprout {
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namespace math {
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namespace detail {
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#if SPROUT_USE_BUILTIN_CMATH_FUNCTION
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inline SPROUT_CONSTEXPR float
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builtin_exp(float x) {
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return __builtin_expf(x);
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}
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inline SPROUT_CONSTEXPR double
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builtin_exp(double x) {
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return __builtin_exp(x);
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}
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inline SPROUT_CONSTEXPR long double
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builtin_exp(long double x) {
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return __builtin_expl(x);
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}
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#endif
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template<typename T>
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inline SPROUT_CONSTEXPR T
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exp_impl_1(T x, std::size_t n, std::size_t last) {
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return last - n == 1
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? sprout::detail::pow_n(x, n) / sprout::math::unchecked_factorial<T>(n)
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: sprout::math::detail::exp_impl_1(x, n, n + (last - n) / 2)
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+ sprout::math::detail::exp_impl_1(x, n + (last - n) / 2, last)
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;
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}
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template<typename T>
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inline SPROUT_CONSTEXPR T
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exp_impl(T x) {
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return !(x > -1) ? T(1) / (T(1) + sprout::math::detail::exp_impl_1(-x, 1, sprout::math::factorial_limit<T>() / 2 + 1))
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: T(1) + sprout::math::detail::exp_impl_1(x, 1, sprout::math::factorial_limit<T>() / 2 + 1)
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;
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}
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} // namespace detail
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//
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// exp
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//
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template<
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typename FloatType,
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typename sprout::enabler_if<std::is_floating_point<FloatType>::value>::type = sprout::enabler
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>
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inline SPROUT_CONSTEXPR FloatType
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exp(FloatType x) {
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return sprout::math::isnan(x) ? x
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: x == -sprout::numeric_limits<FloatType>::infinity() ? FloatType(0)
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: x == sprout::numeric_limits<FloatType>::infinity() ? sprout::numeric_limits<FloatType>::infinity()
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#if SPROUT_USE_BUILTIN_CMATH_FUNCTION
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: sprout::math::detail::builtin_exp(x)
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#else
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: x == 0 ? FloatType(1)
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: static_cast<FloatType>(sprout::math::detail::exp_impl(static_cast<typename sprout::math::detail::float_compute<FloatType>::type>(x)))
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#endif
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;
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}
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template<
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typename IntType,
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typename sprout::enabler_if<std::is_integral<IntType>::value>::type = sprout::enabler
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>
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inline SPROUT_CONSTEXPR double
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exp(IntType x) {
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return sprout::math::exp(static_cast<double>(x));
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}
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} // namespace math
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using sprout::math::exp;
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} // namespace sprout
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#endif // #ifndef SPROUT_MATH_EXP_HPP
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