1 /////////////////////////////////////////////////////////////////////////////// 2 // Copyright 2016 John Maddock. Distributed under the Boost 3 // Software License, Version 1.0. (See accompanying file 4 // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 5 6 #include <boost/multiprecision/cpp_bin_float.hpp> 7 main()8int main() 9 { 10 typedef boost::multiprecision::number<boost::multiprecision::backends::cpp_bin_float<256> > ext_float_t; 11 typedef boost::multiprecision::number<boost::multiprecision::backends::cpp_bin_float<2046> > long_ext_float_t; 12 13 ext_float_t x = 5e15; 14 x += 0.5; 15 ext_float_t x1 = x + 255.0 / (1 << 20); // + 2^-12 - eps 16 ext_float_t x2 = x + 257.0 / (1 << 20); // + 2^-12 + eps 17 double d1 = x1.convert_to<double>(); 18 double d2 = x2.convert_to<double>(); 19 20 std::cout << std::setprecision(18) << d1 << std::endl; 21 std::cout << std::setprecision(18) << d2 << std::endl; 22 23 x = 1e7 + 0.5; 24 x1 = x + ldexp(255.0, -38); // + 2^-30 - eps 25 x2 = x + ldexp(257.0, -38); // + 2^-30 + eps 26 float f1 = x1.convert_to<float>(); 27 float f2 = x2.convert_to<float>(); 28 29 std::cout << std::setprecision(9) << f1 << std::endl; 30 std::cout << std::setprecision(9) << f2 << std::endl; 31 32 long_ext_float_t lf(1); 33 lf += std::numeric_limits<long_ext_float_t>::epsilon(); 34 lf += std::numeric_limits<float>::epsilon() / 2; 35 BOOST_ASSERT(lf != 1); 36 float f3 = lf.convert_to<float>(); 37 std::cout << std::setprecision(9) << f3 << std::endl; 38 39 return (d1 == d2) && (f1 == f2) && (f3 != 1) ? 0 : 1; 40 } 41