math/ccmath/frexp.hpp

0001 //  (C) Copyright Christopher Kormanyos 1999 - 2021.
0002 //  (C) Copyright Matt Borland 2021.
0003 //  Use, modification and distribution are subject to the
0004 //  Boost Software License, Version 1.0. (See accompanying file
0005 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0006
0007 #ifndef BOOST_MATH_CCMATH_FREXP_HPP
0008 #define BOOST_MATH_CCMATH_FREXP_HPP
0009
0010 #include <boost/math/ccmath/detail/config.hpp>
0011
0012 #ifdef BOOST_MATH_NO_CCMATH
0013 #error "The header <boost/math/frexp.hpp> can only be used in C++17 and later."
0014 #endif
0015
0016 #include <boost/math/ccmath/isinf.hpp>
0017 #include <boost/math/ccmath/isnan.hpp>
0018 #include <boost/math/ccmath/isfinite.hpp>
0019
0020 namespace boost::math::ccmath {
0021
0022 namespace detail
0023 {
0024
0025 template <typename Real>
0026 inline constexpr Real frexp_zero_impl(Real arg, int* exp)
0027 {
0028     *exp = 0;
0029     return arg;
0030 }
0031
0032 template <typename Real>
0033 inline constexpr Real frexp_impl(Real arg, int* exp)
0034 {
0035     const bool negative_arg = (arg < Real(0));
0036
0037     Real f = negative_arg ? -arg : arg;
0038     int e2 = 0;
0039     constexpr Real two_pow_32 = Real(4294967296);
0040
0041     while (f >= two_pow_32)
0042     {
0043         f = f / two_pow_32;
0044         e2 += 32;
0045     }
0046
0047     while(f >= Real(1))
0048     {
0049         f = f / Real(2);
0050         ++e2;
0051     }
0052
0053     if(exp != nullptr)
0054     {
0055         *exp = e2;
0056     }
0057
0058     return !negative_arg ? f : -f;
0059 }
0060
0061 } // namespace detail
0062
0063 template <typename Real, std::enable_if_t<!std::is_integral_v<Real>, bool> = true>
0064 inline constexpr Real frexp(Real arg, int* exp)
0065 {
0066     if(BOOST_MATH_IS_CONSTANT_EVALUATED(arg))
0067     {
0068         return arg == Real(0)  ? detail::frexp_zero_impl(arg, exp) :
0069                arg == Real(-0) ? detail::frexp_zero_impl(arg, exp) :
0070                boost::math::ccmath::isinf(arg) ? detail::frexp_zero_impl(arg, exp) :
0071                boost::math::ccmath::isnan(arg) ? detail::frexp_zero_impl(arg, exp) :
0072                boost::math::ccmath::detail::frexp_impl(arg, exp);
0073     }
0074     else
0075     {
0076         using std::frexp;
0077         return frexp(arg, exp);
0078     }
0079 }
0080
0081 template <typename Z, std::enable_if_t<std::is_integral_v<Z>, bool> = true>
0082 inline constexpr double frexp(Z arg, int* exp)
0083 {
0084     return boost::math::ccmath::frexp(static_cast<double>(arg), exp);
0085 }
0086
0087 inline constexpr float frexpf(float arg, int* exp)
0088 {
0089     return boost::math::ccmath::frexp(arg, exp);
0090 }
0091
0092 #ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
0093 inline constexpr long double frexpl(long double arg, int* exp)
0094 {
0095     return boost::math::ccmath::frexp(arg, exp);
0096 }
0097 #endif
0098
0099 }
0100
0101 #endif // BOOST_MATH_CCMATH_FREXP_HPP