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