61 lines
1.8 KiB
C++
61 lines
1.8 KiB
C++
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// (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_ILOGB_HPP
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#define BOOST_MATH_CCMATH_ILOGB_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/ilogb.hpp> can only be used in C++17 and later."
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#endif
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#include <boost/math/ccmath/logb.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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// If arg is not zero, infinite, or NaN, the value returned is exactly equivalent to static_cast<int>(std::logb(arg))
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template <typename Real, std::enable_if_t<!std::is_integral_v<Real>, bool> = true>
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inline constexpr int ilogb(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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return boost::math::ccmath::abs(arg) == Real(0) ? FP_ILOGB0 :
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boost::math::ccmath::isinf(arg) ? INT_MAX :
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boost::math::ccmath::isnan(arg) ? FP_ILOGBNAN :
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static_cast<int>(boost::math::ccmath::logb(arg));
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}
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else
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{
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using std::ilogb;
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return ilogb(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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inline constexpr int ilogb(Z arg) noexcept
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{
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return boost::math::ccmath::ilogb(static_cast<double>(arg));
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}
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inline constexpr int ilogbf(float arg) noexcept
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{
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return boost::math::ccmath::ilogb(arg);
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}
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#ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
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inline constexpr int ilogbl(long double arg) noexcept
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{
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return boost::math::ccmath::ilogb(arg);
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}
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#endif
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} // Namespaces
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#endif // BOOST_MATH_CCMATH_ILOGB_HPP
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