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90 lines
2.6 KiB
C++
90 lines
2.6 KiB
C++
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// Use, modification and distribution are subject to the
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// Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt
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// or copy at http://www.boost.org/LICENSE_1_0.txt)
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// Copyright Paul A. Bristow 2012.
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// Copyright Christopher Kormanyos 2012.
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// This file is written to be included from a Quickbook .qbk document.
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// It can be compiled by the C++ compiler, and run. Any output can
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// also be added here as comment or included or pasted in elsewhere.
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// Caution: this file contains Quickbook markup as well as code
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// and comments: don't change any of the special comment markups!
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#ifdef _MSC_VER
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# pragma warning (disable : 4512) // assignment operator could not be generated.
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# pragma warning (disable : 4996)
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#endif
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//[big_seventh_example_1
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/*`[h5 Using Boost.Multiprecision `cpp_float` for numerical calculations with high precision.]
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The Boost.Multiprecision library can be used for computations requiring precision
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exceeding that of standard built-in types such as float, double
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and long double. For extended-precision calculations, Boost.Multiprecision
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supplies a template data type called cpp_dec_float. The number of decimal
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digits of precision is fixed at compile-time via template parameter.
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To use these floating-point types and constants, we need some includes:
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*/
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#include <boost/math/constants/constants.hpp>
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#include <boost/multiprecision/cpp_dec_float.hpp>
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// using boost::multiprecision::cpp_dec_float
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#include <iostream>
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#include <limits>
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//` So now we can demonstrate with some trivial calculations:
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int main()
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{
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/*`Using `typedef cpp_dec_float_50` hides the complexity of multiprecision to allow us
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to define variables with 50 decimal digit precision just like built-in `double`.
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*/
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using boost::multiprecision::cpp_dec_float_50;
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cpp_dec_float_50 seventh = cpp_dec_float_50(1) / 7;
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/*`By default, output would only show the standard 6 decimal digits,
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so set precision to show all 50 significant digits.
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*/
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std::cout.precision(std::numeric_limits<cpp_dec_float_50>::digits10);
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std::cout << seventh << std::endl;
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/*`which outputs:
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0.14285714285714285714285714285714285714285714285714
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We can also use constants, guaranteed to be initialized with the very last bit of precision.
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*/
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cpp_dec_float_50 circumference = boost::math::constants::pi<cpp_dec_float_50>() * 2 * seventh;
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std::cout << circumference << std::endl;
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/*`which outputs
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0.89759790102565521098932668093700082405633411410717
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*/
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//] [/big_seventh_example_1]
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return 0;
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} // int main()
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/*
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//[big_seventh_example_output
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0.14285714285714285714285714285714285714285714285714
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0.89759790102565521098932668093700082405633411410717
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//]
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*/
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