Initial commit

libs/math/example/policy_ref_snip1.cpp

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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
+*/