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106 lines
3.9 KiB
C++
106 lines
3.9 KiB
C++
// error_policies_example.cpp
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// Copyright Paul A. Bristow 2007, 2010.
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// Copyright John Maddock 2007.
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// Use, modification and distribution are subject to the
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// Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt
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// or copy at http://www.boost.org/LICENSE_1_0.txt)
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#include <boost/math/distributions/normal.hpp>
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using boost::math::normal_distribution;
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#include <boost/math/distributions/students_t.hpp>
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using boost::math::students_t; // Probability of students_t(df, t).
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using boost::math::students_t_distribution;
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// using namespace boost::math; causes:
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//.\error_policy_normal.cpp(30) : error C2872: 'policy' : ambiguous symbol
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// could be '\boost/math/policies/policy.hpp(392) : boost::math::policies::policy'
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// or 'boost::math::policies'
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// So should not use this 'using namespace boost::math;' command.
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// Suppose we want a statistical distribution to return infinities,
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// rather than throw exceptions (the default policy), then we can use:
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// std
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#include <iostream>
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using std::cout;
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using std::endl;
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// using namespace boost::math::policies; or
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using boost::math::policies::policy;
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// Possible errors
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using boost::math::policies::overflow_error;
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using boost::math::policies::underflow_error;
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using boost::math::policies::domain_error;
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using boost::math::policies::pole_error;
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using boost::math::policies::denorm_error;
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using boost::math::policies::evaluation_error;
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using boost::math::policies::ignore_error;
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// Define a custom policy to ignore just overflow:
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typedef policy<
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overflow_error<ignore_error>
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> my_policy;
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// Define another custom policy (perhaps ill-advised?)
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// to ignore all errors: domain, pole, overflow, underflow, denorm & evaluation:
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typedef policy<
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domain_error<ignore_error>,
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pole_error<ignore_error>,
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overflow_error<ignore_error>,
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underflow_error<ignore_error>,
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denorm_error<ignore_error>,
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evaluation_error<ignore_error>
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> my_ignoreall_policy;
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// Define a new distribution with a custom policy to ignore_error
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// (& thus perhaps return infinity for some arguments):
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typedef boost::math::normal_distribution<double, my_policy> my_normal;
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// Note: uses default parameters zero mean and unit standard deviation.
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// We could also do the same for another distribution, for example:
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using boost::math::students_t_distribution;
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typedef students_t_distribution<double, my_ignoreall_policy> my_students_t;
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int main()
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{
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cout << "quantile(my_normal(), 0.05); = " << quantile(my_normal(), 0.05) << endl; // 0.05 is argument within normal range.
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cout << "quantile(my_normal(), 0.); = " << quantile(my_normal(), 0.) << endl; // argument zero, so expect infinity.
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cout << "quantile(my_normal(), 0.); = " << quantile(my_normal(), 0.F) << endl; // argument zero, so expect infinity.
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cout << "quantile(my_students_t(), 0.); = " << quantile(my_students_t(-1), 0.F) << endl; // 'bad' argument negative, so expect NaN.
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#ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
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// Construct a (0, 1) normal distribution that ignores all errors,
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// returning NaN, infinity, zero, or best guess,
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// and NOT setting errno.
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normal_distribution<long double, my_ignoreall_policy> my_normal2(0.L, 1.L); // explicit parameters for distribution.
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cout << "quantile(my_normal2(), 0.); = " << quantile(my_normal2, 0.01) << endl; // argument 0.01, so result finite.
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cout << "quantile(my_normal2(), 0.); = " << quantile(my_normal2, 0.) << endl; // argument zero, so expect infinity.
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#endif
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return 0;
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}
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/*
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Output:
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error_policies_example.cpp
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Generating code
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Finished generating code
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error_policy_normal_example.vcxproj -> J:\Cpp\MathToolkit\test\Math_test\Release\error_policies_example.exe
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quantile(my_normal(), 0.05); = -1.64485
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quantile(my_normal(), 0.); = -1.#INF
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quantile(my_normal(), 0.); = -1.#INF
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quantile(my_students_t(), 0.); = 1.#QNAN
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quantile(my_normal2(), 0.); = -2.32635
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quantile(my_normal2(), 0.); = -1.#INF
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*/
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