585da50d7d
This PR adds the code of Boost.Math as of version 1.89 into the third-party directory, as discussed in a recent RFC [1]. The goal is for this code to be used as a back-end for the C++17 Math Special Functions. As explained in third-paty/README.md, this code is cleared for usage inside libc++ for the Math Special functions, however the LLVM Foundation should be consulted before using this code anywhere else in the LLVM project, due to the fact that it is under the Boost Software License (as opposed to the usual LLVM license). See the RFC [1] for more details. [1]: https://discourse.llvm.org/t/rfc-libc-taking-a-dependency-on-boost-math-for-the-c-17-math-special-functions
87 lines
2.3 KiB
C++
87 lines
2.3 KiB
C++
// (C) Copyright Matt Borland 2021.
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// Use, modification and distribution are subject to the
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// Boost Software License, Version 1.0. (See accompanying file
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// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_MATH_CCMATH_LOGB_HPP
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#define BOOST_MATH_CCMATH_LOGB_HPP
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#include <boost/math/ccmath/detail/config.hpp>
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#ifdef BOOST_MATH_NO_CCMATH
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#error "The header <boost/math/logb.hpp> can only be used in C++17 and later."
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#endif
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#include <boost/math/ccmath/frexp.hpp>
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#include <boost/math/ccmath/isinf.hpp>
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#include <boost/math/ccmath/isnan.hpp>
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#include <boost/math/ccmath/abs.hpp>
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namespace boost::math::ccmath {
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namespace detail {
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// The value of the exponent returned by std::logb is always 1 less than the exponent returned by
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// std::frexp because of the different normalization requirements: for the exponent e returned by std::logb,
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// |arg*r^-e| is between 1 and r (typically between 1 and 2), but for the exponent e returned by std::frexp,
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// |arg*2^-e| is between 0.5 and 1.
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template <typename T>
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constexpr T logb_impl(T arg) noexcept
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{
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int exp = 0;
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boost::math::ccmath::frexp(arg, &exp);
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return static_cast<T>(exp - 1);
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}
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} // Namespace detail
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template <typename Real, std::enable_if_t<!std::is_integral_v<Real>, bool> = true>
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constexpr Real logb(Real arg) noexcept
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{
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if(BOOST_MATH_IS_CONSTANT_EVALUATED(arg))
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{
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if (boost::math::ccmath::abs(arg) == Real(0))
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{
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return -std::numeric_limits<Real>::infinity();
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}
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else if (boost::math::ccmath::isinf(arg))
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{
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return std::numeric_limits<Real>::infinity();
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}
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else if (boost::math::ccmath::isnan(arg))
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{
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return arg;
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}
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return boost::math::ccmath::detail::logb_impl(arg);
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}
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else
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{
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using std::logb;
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return logb(arg);
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}
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}
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template <typename Z, std::enable_if_t<std::is_integral_v<Z>, bool> = true>
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constexpr double logb(Z arg) noexcept
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{
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return boost::math::ccmath::logb(static_cast<double>(arg));
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}
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constexpr float logbf(float arg) noexcept
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{
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return boost::math::ccmath::logb(arg);
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}
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#ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
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constexpr long double logbl(long double arg) noexcept
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{
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return boost::math::ccmath::logb(arg);
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}
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#endif
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} // Namespaces
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#endif // BOOST_MATH_CCMATH_LOGB_HPP
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