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// example_policy_handling.cpp
// Copyright Paul A. Bristow 2007.
// Copyright John Maddock 2007.
// Use, modification and distribution are subject to the
// Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt
// or copy at http://www.boost.org/LICENSE_1_0.txt)
// See error_handling_example.cpp for use of
// macro definition to change policy for
// domain_error - negative degrees of freedom argument
// for student's t distribution CDF,
// and catching the exception.
// See error_handling_policies for more examples.
// Boost
#include <boost/math/distributions/students_t.hpp>
using boost::math::students_t_distribution; // Probability of students_t(df, t).
using boost::math::students_t; // Probability of students_t(df, t) convenience typedef for double.
// std
#include <iostream>
using std::cout;
using std::endl;
#include <stdexcept>
using std::exception;
using boost::math::policies::policy;
using boost::math::policies::domain_error;
using boost::math::policies::ignore_error;
// Define a (bad?) policy to ignore domain errors ('bad' arguments):
typedef policy<
domain_error<ignore_error>
> my_policy;
// Define my distribution with this different domain error policy:
typedef students_t_distribution<double, my_policy> my_students_t;
int main()
{ // Example of error handling of bad argument(s) to a distribution.
cout << "Example error handling using Student's t function. " << endl;
double degrees_of_freedom = -1; double t = -1.; // Two 'bad' arguments!
try
{
cout << "Probability of ignore_error Student's t is " << cdf(my_students_t(degrees_of_freedom), t) << endl;
cout << "Probability of default error policy Student's t is " << endl;
// BY contrast the students_t distribution default domain error policy is to throw,
cout << cdf(students_t(-1), -1) << endl; // so this will throw.
/*`
Message from thrown exception was:
Error in function boost::math::students_t_distribution<double>::students_t_distribution:
Degrees of freedom argument is -1, but must be > 0 !
*/
// We could also define a 'custom' distribution
// with an "ignore overflow error policy" in a single statement:
using boost::math::policies::overflow_error;
students_t_distribution<double, policy<overflow_error<ignore_error> > > students_t_no_throw(-1);
}
catch(const std::exception& e)
{
std::cout <<
"\n""Message from thrown exception was:\n " << e.what() << std::endl;
}
return 0;
} // int main()
/*
Output:
Example error handling using Student's t function.
Probability of ignore_error Student's t is 1.#QNAN
Probability of default error policy Student's t is
Message from thrown exception was:
Error in function boost::math::students_t_distribution<double>::students_t_distribution:
Degrees of freedom argument is -1, but must be > 0 !
*/
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