ceph/src/boost/libs/math/example/policy_ref_snip9.cpp

   1 //  Copyright John Maddock 2007.
   2 //  Copyright Paul A. Bristow 2010
   3
   4 //  Use, modification and distribution are subject to the
   5 //  Boost Software License, Version 1.0. (See accompanying file
   6 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   7
   8 // Note that this file contains quickbook mark-up as well as code
   9 // and comments, don't change any of the special comment mark-ups!
  10
  11 #include <iostream>
  12 using std::cout; using std::endl;
  13
  14 //[policy_ref_snip9
  15
  16 #include <boost/math/special_functions/gamma.hpp>
  17 using boost::math::tgamma;
  18 using boost::math::policies::policy;
  19 using boost::math::policies::digits10;
  20
  21 typedef policy<digits10<5> > my_pol_5; // Define a new, non-default, policy
  22 // to calculate tgamma to accuracy of approximately 5 decimal digits.
  23 //]
  24
  25 int main()
  26 {
  27   cout.precision(5); // To only show 5 (hopefully) accurate decimal digits.
  28   double t = tgamma(12, my_pol_5()); // Apply the 5 decimal digits accuracy policy to use of tgamma.
  29   cout << "tgamma(12, my_pol_5() = " << t << endl;
  30 }
  31
  32 /*
  33
  34 Output:
  35      tgamma(12, my_pol_5() = 3.9917e+007
  36 */