ceph/src/boost/libs/math/example/big_seventh.cpp

   1
   2 // Use, modification and distribution are subject to the
   3 // Boost Software License, Version 1.0.
   4 // (See accompanying file LICENSE_1_0.txt
   5 // or copy at http://www.boost.org/LICENSE_1_0.txt)
   6
   7 // Copyright Paul A. Bristow 2012.
   8 // Copyright Christopher Kormanyos 2012.
   9
  10 // This file is written to be included from a Quickbook .qbk document.
  11 // It can be compiled by the C++ compiler, and run. Any output can
  12 // also be added here as comment or included or pasted in elsewhere.
  13 // Caution: this file contains Quickbook markup as well as code
  14 // and comments: don't change any of the special comment markups!
  15
  16 #ifdef _MSC_VER
  17 #  pragma warning (disable : 4512) // assignment operator could not be generated.
  18 #  pragma warning (disable : 4996)
  19 #endif
  20
  21 //[big_seventh_example_1
  22
  23 /*`[h5 Using Boost.Multiprecision `cpp_float` for numerical calculations with high precision.]
  24
  25 The Boost.Multiprecision library can be used for computations requiring precision
  26 exceeding that of standard built-in types such as float, double
  27 and long double. For extended-precision calculations, Boost.Multiprecision
  28 supplies a template data type called cpp_dec_float. The number of decimal
  29 digits of precision is fixed at compile-time via template parameter.
  30
  31 To use these floating-point types and constants, we need some includes:
  32
  33 */
  34
  35 #include <boost/math/constants/constants.hpp>
  36
  37 #include <boost/multiprecision/cpp_dec_float.hpp>
  38 // using boost::multiprecision::cpp_dec_float
  39
  40 #include <iostream>
  41 #include <limits>
  42
  43 //` So now we can demonstrate with some trivial calculations:
  44
  45 int main()
  46 {
  47 /*`Using `typedef cpp_dec_float_50` hides the complexity of multiprecision to allow us
  48   to define variables with 50 decimal digit precision just like built-in `double`.
  49 */
  50   using boost::multiprecision::cpp_dec_float_50;
  51
  52   cpp_dec_float_50 seventh = cpp_dec_float_50(1) / 7;
  53
  54   /*`By default, output would only show the standard 6 decimal digits,
  55      so set precision to show all 50 significant digits.
  56   */
  57   std::cout.precision(std::numeric_limits<cpp_dec_float_50>::digits10);
  58   std::cout << seventh << std::endl;
  59 /*`which outputs:
  60
  61   0.14285714285714285714285714285714285714285714285714
  62
  63 We can also use constants, guaranteed to be initialized with the very last bit of precision.
  64 */
  65
  66   cpp_dec_float_50 circumference = boost::math::constants::pi<cpp_dec_float_50>() * 2 * seventh;
  67
  68   std::cout << circumference << std::endl;
  69
  70 /*`which outputs
  71
  72     0.89759790102565521098932668093700082405633411410717
  73 */
  74 //]  [/big_seventh_example_1]
  75
  76     return 0;
  77 } // int main()
  78
  79
  80 /*
  81 //[big_seventh_example_output
  82
  83   0.14285714285714285714285714285714285714285714285714
  84   0.89759790102565521098932668093700082405633411410717
  85
  86 //]
  87
  88 */
  89