87 lines
2.3 KiB
C++
87 lines
2.3 KiB
C++
// (C) Copyright Matt Borland 2021.
|
|
// Use, modification and distribution are subject to the
|
|
// Boost Software License, Version 1.0. (See accompanying file
|
|
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
|
|
|
|
#ifndef BOOST_MATH_CCMATH_LOGB_HPP
|
|
#define BOOST_MATH_CCMATH_LOGB_HPP
|
|
|
|
#include <boost/math/ccmath/detail/config.hpp>
|
|
|
|
#ifdef BOOST_MATH_NO_CCMATH
|
|
#error "The header <boost/math/logb.hpp> can only be used in C++17 and later."
|
|
#endif
|
|
|
|
#include <boost/math/ccmath/frexp.hpp>
|
|
#include <boost/math/ccmath/isinf.hpp>
|
|
#include <boost/math/ccmath/isnan.hpp>
|
|
#include <boost/math/ccmath/abs.hpp>
|
|
|
|
namespace boost::math::ccmath {
|
|
|
|
namespace detail {
|
|
|
|
// The value of the exponent returned by std::logb is always 1 less than the exponent returned by
|
|
// std::frexp because of the different normalization requirements: for the exponent e returned by std::logb,
|
|
// |arg*r^-e| is between 1 and r (typically between 1 and 2), but for the exponent e returned by std::frexp,
|
|
// |arg*2^-e| is between 0.5 and 1.
|
|
template <typename T>
|
|
constexpr T logb_impl(T arg) noexcept
|
|
{
|
|
int exp = 0;
|
|
boost::math::ccmath::frexp(arg, &exp);
|
|
|
|
return static_cast<T>(exp - 1);
|
|
}
|
|
|
|
} // Namespace detail
|
|
|
|
template <typename Real, std::enable_if_t<!std::is_integral_v<Real>, bool> = true>
|
|
constexpr Real logb(Real arg) noexcept
|
|
{
|
|
if(BOOST_MATH_IS_CONSTANT_EVALUATED(arg))
|
|
{
|
|
if (boost::math::ccmath::abs(arg) == Real(0))
|
|
{
|
|
return -std::numeric_limits<Real>::infinity();
|
|
}
|
|
else if (boost::math::ccmath::isinf(arg))
|
|
{
|
|
return std::numeric_limits<Real>::infinity();
|
|
}
|
|
else if (boost::math::ccmath::isnan(arg))
|
|
{
|
|
return arg;
|
|
}
|
|
|
|
return boost::math::ccmath::detail::logb_impl(arg);
|
|
}
|
|
else
|
|
{
|
|
using std::logb;
|
|
return logb(arg);
|
|
}
|
|
}
|
|
|
|
template <typename Z, std::enable_if_t<std::is_integral_v<Z>, bool> = true>
|
|
constexpr double logb(Z arg) noexcept
|
|
{
|
|
return boost::math::ccmath::logb(static_cast<double>(arg));
|
|
}
|
|
|
|
constexpr float logbf(float arg) noexcept
|
|
{
|
|
return boost::math::ccmath::logb(arg);
|
|
}
|
|
|
|
#ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
|
|
constexpr long double logbl(long double arg) noexcept
|
|
{
|
|
return boost::math::ccmath::logb(arg);
|
|
}
|
|
#endif
|
|
|
|
} // Namespaces
|
|
|
|
#endif // BOOST_MATH_CCMATH_LOGB_HPP
|