Initial commit

libs/math/example/policy_ref_snip12.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!
+
+// Define tgamma function with a no overflow policy
+// into a specific namespace-scope.
+
+#include <iostream>
+using std::cout; using std::endl;
+
+//[policy_ref_snip12
+
+#include <boost/math/special_functions/gamma.hpp>
+//using boost::math::tgamma;
+// Need not declare using boost::math::tgamma here,
+// because will define tgamma in myspace using macro below.
+
+namespace myspace
+{
+  using namespace boost::math::policies;
+
+  // Define a policy that does not throw on overflow:
+  typedef policy<overflow_error<errno_on_error> > my_policy;
+
+  // Define the special functions in this scope to use the policy:   
+  BOOST_MATH_DECLARE_SPECIAL_FUNCTIONS(my_policy)
+}
+
+// Now we can use myspace::tgamma etc.
+// They will automatically use "my_policy":
+//
+double t = myspace::tgamma(30.0); // Will *not* throw on overflow,
+// despite the large value of factorial 30 = 265252859812191058636308480000000
+// unlike default policy boost::math::tgamma;
+
+//]
+
+int main()
+{
+   cout << "myspace::tgamma(30.0) = " << t << endl;
+}
+
+/*
+
+Output:
+
+myspace::tgamma(30.0) = 8.84176e+030
+
+*/
+