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https://github.com/bolero-MURAKAMI/Sprout.git
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82 lines
2.1 KiB
C++
82 lines
2.1 KiB
C++
#ifndef SPROUT_MATH_LOG_HPP
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#define SPROUT_MATH_LOG_HPP
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#include <cstddef>
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#include <limits>
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#include <type_traits>
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#include <sprout/config.hpp>
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#include <sprout/math/constants.hpp>
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#include <sprout/math/factorial.hpp>
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#include <sprout/math/sqrt.hpp>
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#include <sprout/type_traits/enabler_if.hpp>
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#if SPROUT_USE_BUILTIN_CMATH_FUNCTION
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# include <cmath>
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#endif
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namespace sprout {
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namespace math {
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namespace detail {
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template<typename T>
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inline SPROUT_CONSTEXPR T
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log_impl_2(T x, T tmp, std::size_t n, T xn) {
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return n > sprout::math::factorial_limit<T>() ? tmp
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: sprout::math::detail::log_impl_2(
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x,
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tmp + (n % 2 ? 1 : -1) * xn / n,
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n + 1,
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xn * x
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)
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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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log_impl_1(T x) {
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return sprout::math::detail::log_impl_2(
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x,
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x,
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2,
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x * x
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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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log_impl(T x) {
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return !(x > sprout::math::root_two<T>()) ? sprout::math::detail::log_impl_1(x - 1)
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: 2 * sprout::math::detail::log_impl(sprout::math::sqrt(x))
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;
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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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log(FloatType x) {
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typedef double type;
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return x == 0 ? std::numeric_limits<FloatType>::quiet_NaN()
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: !(x > 0) ? -std::numeric_limits<FloatType>::infinity()
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: static_cast<FloatType>(sprout::math::detail::log_impl(x))
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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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log(IntType x) {
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return sprout::math::detail::log(static_cast<double>(x));
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}
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} // namespace detail
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# if SPROUT_USE_BUILTIN_CMATH_FUNCTION
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using std::log;
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# else
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using sprout::math::detail::log;
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# endif
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} // namespace math
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using sprout::math::log;
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} // namespace sprout
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#endif // #ifndef SPROUT_MATH_LOG_HPP
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