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

   1 // error_policies_example.cpp
   2
   3 // Copyright Paul A. Bristow 2007, 2010.
   4 // Copyright John Maddock 2007.
   5
   6 // Use, modification and distribution are subject to the
   7 // Boost Software License, Version 1.0.
   8 // (See accompanying file LICENSE_1_0.txt
   9 // or copy at http://www.boost.org/LICENSE_1_0.txt)
  10
  11 #include <boost/math/distributions/normal.hpp>
  12   using boost::math::normal_distribution;
  13
  14 #include <boost/math/distributions/students_t.hpp>
  15    using boost::math::students_t;  // Probability of students_t(df, t).
  16    using boost::math::students_t_distribution;
  17
  18 //  using namespace boost::math; causes:
  19 //.\error_policy_normal.cpp(30) : error C2872: 'policy' : ambiguous symbol
  20 //        could be '\boost/math/policies/policy.hpp(392) : boost::math::policies::policy'
  21 //        or 'boost::math::policies'
  22
  23 // So should not use this 'using namespace boost::math;' command.
  24
  25 // Suppose we want a statistical distribution to return infinities,
  26 // rather than throw exceptions (the default policy), then we can use:
  27
  28 // std
  29 #include <iostream>
  30    using std::cout;
  31    using std::endl;
  32
  33 // using namespace boost::math::policies; or
  34
  35 using boost::math::policies::policy;
  36 // Possible errors
  37 using boost::math::policies::overflow_error;
  38 using boost::math::policies::underflow_error;
  39 using boost::math::policies::domain_error;
  40 using boost::math::policies::pole_error;
  41 using boost::math::policies::denorm_error;
  42 using boost::math::policies::evaluation_error;
  43 using boost::math::policies::ignore_error;
  44
  45 // Define a custom policy to ignore just overflow:
  46 typedef policy<
  47 overflow_error<ignore_error>
  48       > my_policy;
  49
  50 // Define another custom policy (perhaps ill-advised?)
  51 // to ignore all errors: domain, pole, overflow, underflow, denorm & evaluation:
  52 typedef policy<
  53 domain_error<ignore_error>,
  54 pole_error<ignore_error>,
  55 overflow_error<ignore_error>,
  56 underflow_error<ignore_error>,
  57 denorm_error<ignore_error>,
  58 evaluation_error<ignore_error>
  59       > my_ignoreall_policy;
  60
  61 // Define a new distribution with a custom policy to ignore_error
  62 // (& thus perhaps return infinity for some arguments):
  63 typedef boost::math::normal_distribution<double, my_policy> my_normal;
  64 // Note: uses default parameters zero mean and unit standard deviation.
  65
  66 // We could also do the same for another distribution, for example:
  67 using boost::math::students_t_distribution;
  68 typedef students_t_distribution<double, my_ignoreall_policy> my_students_t;
  69
  70 int main()
  71 {
  72   cout << "quantile(my_normal(), 0.05); = " << quantile(my_normal(), 0.05) << endl; // 0.05 is argument within normal range.
  73   cout << "quantile(my_normal(), 0.); = " << quantile(my_normal(), 0.) << endl; // argument zero, so expect infinity.
  74   cout << "quantile(my_normal(), 0.); = " << quantile(my_normal(), 0.F) << endl; // argument zero, so expect infinity.
  75
  76   cout << "quantile(my_students_t(), 0.); = " << quantile(my_students_t(-1), 0.F) << endl; // 'bad' argument negative, so expect NaN.
  77
  78 #ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
  79   // Construct a (0, 1) normal distribution that ignores all errors,
  80   // returning NaN, infinity, zero, or best guess,
  81   // and NOT setting errno.
  82   normal_distribution<long double, my_ignoreall_policy> my_normal2(0.L, 1.L); // explicit parameters for distribution.
  83   cout << "quantile(my_normal2(), 0.); = " << quantile(my_normal2, 0.01) << endl; // argument 0.01, so result finite.
  84   cout << "quantile(my_normal2(), 0.); = " << quantile(my_normal2, 0.) << endl; // argument zero, so expect infinity.
  85 #endif
  86
  87   return 0;
  88 }
  89
  90 /*
  91
  92 Output:
  93
  94 error_policies_example.cpp
  95   Generating code
  96   Finished generating code
  97   error_policy_normal_example.vcxproj -> J:\Cpp\MathToolkit\test\Math_test\Release\error_policies_example.exe
  98   quantile(my_normal(), 0.05); = -1.64485
  99   quantile(my_normal(), 0.); = -1.#INF
 100   quantile(my_normal(), 0.); = -1.#INF
 101   quantile(my_students_t(), 0.); = 1.#QNAN
 102   quantile(my_normal2(), 0.); = -2.32635
 103   quantile(my_normal2(), 0.); = -1.#INF
 104
 105 */