ceph/src/boost/libs/math/example/policy_ref_snip13.cpp

   1 //  Copyright John Maddock 2007.
   2 //  Copyright Paul A. Bristow 2010
   3 //  Use, modification and distribution are subject to the
   4 //  Boost Software License, Version 1.0. (See accompanying file
   5 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6
   7 // Note that this file contains quickbook mark-up as well as code
   8 // and comments, don't change any of the special comment mark-ups!
   9
  10 #ifdef _MSC_VER
  11 #  pragma warning (disable : 4189) //  'd' : local variable is initialized but not referenced
  12 #endif
  13
  14 #include <iostream>
  15 using std::cout; using std::endl;
  16
  17 #include <stdexcept>
  18 using std::domain_error;
  19
  20 //[policy_ref_snip13
  21
  22 #include <boost/math/distributions/cauchy.hpp>
  23
  24 namespace myspace
  25 { // using namespace boost::math::policies; // May be convenient in myspace.
  26
  27   // Define a policy called my_policy to use.
  28   using boost::math::policies::policy;
  29
  30 // In this case we want all the distribution accessor functions to compile,
  31 // even if they are mathematically undefined, so
  32 // make the policy assert_undefined.
  33   using boost::math::policies::assert_undefined;
  34
  35 typedef policy<assert_undefined<false> > my_policy;
  36
  37 // Finally apply this policy to type double.
  38 BOOST_MATH_DECLARE_DISTRIBUTIONS(double, my_policy)
  39 } // namespace myspace
  40
  41 // Now we can use myspace::cauchy etc, which will use policy
  42 // myspace::mypolicy:
  43 //
  44 // This compiles but throws a domain error exception at runtime.
  45 // Caution! If you omit the try'n'catch blocks,
  46 // it will just silently terminate, giving no clues as to why!
  47 // So try'n'catch blocks are very strongly recommended.
  48
  49 void test_cauchy()
  50 {
  51    try
  52    {
  53       double d = mean(myspace::cauchy());  // Cauchy does not have a mean!
  54    }
  55    catch(const std::domain_error& e)
  56    {
  57       cout << e.what() << endl;
  58    }
  59 }
  60
  61 //] //[/policy_ref_snip13]
  62
  63 int main()
  64 {
  65    test_cauchy();
  66 }
  67
  68 /*
  69
  70 Output:
  71
  72 policy_snip_13.vcxproj -> J:\Cpp\MathToolkit\test\Math_test\Release\policy_snip_13.exe
  73   Error in function boost::math::mean(cauchy<double>&): The Cauchy distribution does not have a mean: the only possible return value is 1.#QNAN.
  74
  75   */
  76