libs/math/example/big_seventh.cpp

// 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)

// Copyright Paul A. Bristow 2012.
// Copyright Christopher Kormanyos 2012.

// This file is written to be included from a Quickbook .qbk document.
// It can be compiled by the C++ compiler, and run. Any output can
// also be added here as comment or included or pasted in elsewhere.
// Caution: this file contains Quickbook markup as well as code
// and comments: don't change any of the special comment markups!

#ifdef _MSC_VER
#  pragma warning (disable : 4512) // assignment operator could not be generated.
#  pragma warning (disable : 4996)
#endif

//[big_seventh_example_1

/*`[h5 Using Boost.Multiprecision `cpp_float` for numerical calculations with high precision.]

The Boost.Multiprecision library can be used for computations requiring precision
exceeding that of standard built-in types such as float, double
and long double. For extended-precision calculations, Boost.Multiprecision
supplies a template data type called cpp_dec_float. The number of decimal
digits of precision is fixed at compile-time via template parameter.

To use these floating-point types and constants, we need some includes:

*/

#include <boost/math/constants/constants.hpp>

#include <boost/multiprecision/cpp_dec_float.hpp>
// using boost::multiprecision::cpp_dec_float

#include <iostream>
#include <limits>

/*` So now we can demonstrate with some trivial calculations:
*/

//] //[big_seventh_example_1]

int main()
{

//[big_seventh_example_2
/*`Using `typedef cpp_dec_float_50` hides the complexity of multiprecision,
allows us  to define variables with 50 decimal digit precision just like built-in `double`.
*/
  using boost::multiprecision::cpp_dec_float_50;

  cpp_dec_float_50 seventh = cpp_dec_float_50(1) / 7;  // 1 / 7

/*`By default, output would only show the standard 6 decimal digits,
 so set precision to show all 50 significant digits, including any trailing zeros.
*/
  std::cout.precision(std::numeric_limits<cpp_dec_float_50>::digits10);
  std::cout << std::showpoint << std::endl; // Append any trailing zeros.
  std::cout << seventh << std::endl;
/*`which outputs:

  0.14285714285714285714285714285714285714285714285714

We can also use Boost.Math __constants like [pi],
guaranteed to be initialized with the very last bit of precision for the floating-point type.
*/

   std::cout << "pi = " << boost::math::constants::pi<cpp_dec_float_50>() << std::endl;
   cpp_dec_float_50 circumference = boost::math::constants::pi<cpp_dec_float_50>() * 2 * seventh;
   std::cout << "c =  "<< circumference << std::endl;

/*`which outputs

  pi = 3.1415926535897932384626433832795028841971693993751

  c =  0.89759790102565521098932668093700082405633411410717
*/
//]  [/big_seventh_example_2]

    return 0;
} // int main()


/*
//[big_seventh_example_output

0.14285714285714285714285714285714285714285714285714
pi = 3.1415926535897932384626433832795028841971693993751
c =  0.89759790102565521098932668093700082405633411410717

//] //[big_seventh_example_output]

*/
Boost C++ Libraries

libs/math/example/big_seventh.cpp
