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libs/math/example/big_seventh.cpp

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+
+// 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:
+
+int main()
+{
+/*`Using `typedef cpp_dec_float_50` hides the complexity of multiprecision to allow 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;
+
+  /*`By default, output would only show the standard 6 decimal digits,
+     so set precision to show all 50 significant digits.
+  */
+  std::cout.precision(std::numeric_limits<cpp_dec_float_50>::digits10);
+  std::cout << seventh << std::endl;
+/*`which outputs:
+
+  0.14285714285714285714285714285714285714285714285714
+
+We can also use constants, guaranteed to be initialized with the very last bit of precision.
+*/
+
+  cpp_dec_float_50 circumference = boost::math::constants::pi<cpp_dec_float_50>() * 2 * seventh;
+
+  std::cout << circumference << std::endl;
+
+/*`which outputs
+
+    0.89759790102565521098932668093700082405633411410717
+*/
+//]  [/big_seventh_example_1]
+
+    return 0;
+} // int main()
+
+
+/*
+//[big_seventh_example_output
+
+  0.14285714285714285714285714285714285714285714285714
+  0.89759790102565521098932668093700082405633411410717
+
+//]
+
+*/
+