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76 lines
2.4 KiB
C++
76 lines
2.4 KiB
C++
// Copyright John Maddock 2007.
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// Copyright Paul A. Bristow 2010.
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// Use, modification and distribution are subject to the
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// Boost Software License, Version 1.0. (See accompanying file
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// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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// Note that this file contains quickbook mark-up as well as code
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// and comments, don't change any of the special comment mark-ups!
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//[policy_ref_snip1
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#include <boost/math/special_functions/gamma.hpp>
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using boost::math::tgamma;
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//using namespace boost::math::policies; may also be convenient.
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using boost::math::policies::policy;
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using boost::math::policies::evaluation_error;
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using boost::math::policies::domain_error;
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using boost::math::policies::overflow_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::errno_on_error;
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// Define a policy:
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typedef policy<
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domain_error<errno_on_error>,
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pole_error<errno_on_error>,
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overflow_error<errno_on_error>,
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evaluation_error<errno_on_error>
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> my_policy;
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double my_value = 0.; //
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// Call the function applying my_policy:
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double t1 = tgamma(my_value, my_policy());
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// Alternatively (and equivalently) we could use helpful function
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// make_policy and define everything at the call site:
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double t2 = tgamma(my_value,
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make_policy(
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domain_error<errno_on_error>(),
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pole_error<errno_on_error>(),
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overflow_error<errno_on_error>(),
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evaluation_error<errno_on_error>() )
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);
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//]
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#include <iostream>
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using std::cout; using std::endl;
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int main()
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{
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cout << "my_value = " << my_value << endl;
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try
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{ // First with default policy - throw an exception.
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cout << "tgamma(my_value) = " << tgamma(my_value) << endl;
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}
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catch(const std::exception& e)
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{
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cout <<"\n""Message from thrown exception was:\n " << e.what() << endl;
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}
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cout << "tgamma(my_value, my_policy() = " << t1 << endl;
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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;
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}
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/*
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Output:
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my_value = 0
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Message from thrown exception was:
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Error in function boost::math::tgamma<long double>(long double): Evaluation of tgamma at a negative integer 0.
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tgamma(my_value, my_policy() = 1.#QNAN
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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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*/
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