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// C_error_policy_example.cpp
// Copyright Paul A. Bristow 2007, 2010.
// 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)
// Suppose we want a call to tgamma to behave in a C-compatible way
// and set global ::errno rather than throw an exception.
#include <cerrno> // for ::errno
#include <boost/math/special_functions/gamma.hpp>
using boost::math::tgamma;
using boost::math::policies::policy;
// Possible errors
using boost::math::policies::overflow_error;
using boost::math::policies::underflow_error;
using boost::math::policies::domain_error;
using boost::math::policies::pole_error;
using boost::math::policies::denorm_error;
using boost::math::policies::evaluation_error;
using boost::math::policies::errno_on_error;
using boost::math::policies::ignore_error;
//using namespace boost::math::policies;
//using namespace boost::math; // avoid potential ambiguity with std:: <random>
// Define a policy:
typedef policy<
domain_error<errno_on_error>, // 'bad' arguments.
pole_error<errno_on_error>, // argument is pole value.
overflow_error<errno_on_error>, // argument value causes overflow.
evaluation_error<errno_on_error> // evaluation does not converge and may be inaccurate, or worse,
// or there is no way known (yet) to implement this evaluation,
// for example, kurtosis of non-central beta distribution.
> C_error_policy;
// std
#include <iostream>
using std::cout;
using std::endl;
int main()
{
// We can achieve this at the function call site
// with the previously defined policy C_error_policy.
double t = tgamma(4., C_error_policy());
cout << "tgamma(4., C_error_policy() = " << t << endl; // 6
// Alternatively we could use the function make_policy,
// provided for convenience,
// and define everything at the call site:
t = tgamma(4., make_policy(
domain_error<errno_on_error>(),
pole_error<errno_on_error>(),
overflow_error<errno_on_error>(),
evaluation_error<errno_on_error>()
));
cout << "tgamma(4., make_policy(...) = " << t << endl; // 6
return 0;
} // int main()
/*
Output
c_error_policy_example.cpp
Generating code
Finished generating code
c_error_policy_example.vcxproj -> J:\Cpp\MathToolkit\test\Math_test\Release\c_error_policy_example.exe
tgamma(4., C_error_policy() = 6
tgamma(4., make_policy(...) = 6
tgamma(4., C_error_policy() = 6
tgamma(4., make_policy(...) = 6
*/
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