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- // Copyright John Maddock 2007.
- // Copyright Paul A. Bristow 2010.
- // 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)
- // Note that this file contains quickbook mark-up as well as code
- // and comments, don't change any of the special comment mark-ups!
- //[policy_ref_snip1
- #include <boost/math/special_functions/gamma.hpp>
- using boost::math::tgamma;
- //using namespace boost::math::policies; may also be convenient.
- using boost::math::policies::policy;
- using boost::math::policies::evaluation_error;
- using boost::math::policies::domain_error;
- using boost::math::policies::overflow_error;
- using boost::math::policies::domain_error;
- using boost::math::policies::pole_error;
- using boost::math::policies::errno_on_error;
- // Define a policy:
- typedef policy<
- domain_error<errno_on_error>,
- pole_error<errno_on_error>,
- overflow_error<errno_on_error>,
- evaluation_error<errno_on_error>
- > my_policy;
- double my_value = 0.; //
- // Call the function applying my_policy:
- double t1 = tgamma(my_value, my_policy());
- // Alternatively (and equivalently) we could use helpful function
- // make_policy and define everything at the call site:
- double t2 = tgamma(my_value,
- make_policy(
- domain_error<errno_on_error>(),
- pole_error<errno_on_error>(),
- overflow_error<errno_on_error>(),
- evaluation_error<errno_on_error>() )
- );
- //]
- #include <iostream>
- using std::cout; using std::endl;
- int main()
- {
- cout << "my_value = " << my_value << endl;
- try
- { // First with default policy - throw an exception.
- cout << "tgamma(my_value) = " << tgamma(my_value) << endl;
- }
- catch(const std::exception& e)
- {
- cout <<"\n""Message from thrown exception was:\n " << e.what() << endl;
- }
- cout << "tgamma(my_value, my_policy() = " << t1 << endl;
- cout << "tgamma(my_value, make_policy(domain_error<errno_on_error>(), pole_error<errno_on_error>(), overflow_error<errno_on_error>(), evaluation_error<errno_on_error>() ) = " << t2 << endl;
- }
- /*
- Output:
- my_value = 0
-
- Message from thrown exception was:
- Error in function boost::math::tgamma<long double>(long double): Evaluation of tgamma at a negative integer 0.
- tgamma(my_value, my_policy() = 1.#QNAN
- tgamma(my_value, make_policy(domain_error<errno_on_error>(), pole_error<errno_on_error>(), overflow_error<errno_on_error>(), evaluation_error<errno_on_error>() ) = 1.#QNAN
- */
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