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

   1 // Copyright Paul A. Bristow 2018
   2
   3 // Distributed under the 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 // Example of most basic call of both lambert W functions.
   8 // Only requires C++03
   9 // (and optionally a call of max_digits10 to show precision).
  10
  11 #include <boost/math/special_functions/lambert_w.hpp> // For lambert_w0 and wm1 functions.
  12
  13 #include <iostream>
  14 #include <iomanip>
  15
  16 int main()
  17 {
  18   double z = 2.0;
  19   double w0 = boost::math::lambert_w0(z);
  20   std::cout.setf(std::ios_base::showpoint); // Include any trailing zeros.
  21   std::cout.precision(std::numeric_limits<double>::max_digits10); // Show all possibly significant digits.
  22   // Avoid using max_digfigs10 so as many old compilers can run the most basic lambert_w0 test?
  23   // Require to get max_digits10
  24   //   [ run lambert_w_basic_example.cpp  : : : [ requires cxx11_numeric_limits ] ]
  25   std::cout << " lambert_w0(" << z << ") = " << w0 << std::endl; // lambert_w0(2.00000) = 0.852606
  26   z = -0.2;
  27   double wm1 = boost::math::lambert_wm1(z);
  28   std::cout << " lambert_wm1(" << z << ") = " << wm1 << std::endl; // lambert_wm1(-0.200000) = -2.54264
  29   return 0;
  30 } // int main()