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
main()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 */
106