mirror of
https://github.com/boostorg/math.git
synced 2026-01-24 18:12:09 +00:00
120 lines
3.1 KiB
C++
120 lines
3.1 KiB
C++
// Copyright John Maddock 2007.
|
|
// 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!
|
|
|
|
#include <iostream>
|
|
|
|
//[policy_eg_6
|
|
|
|
/*`
|
|
Suppose we want a set of distributions to behave as follows:
|
|
|
|
* Return infinity on overflow, rather than throwing an exception.
|
|
* Don't perform any promotion from double to long double internally.
|
|
* Return the closest integer result from the quantiles of discrete
|
|
distributions.
|
|
|
|
We'll begin by including the needed header:
|
|
*/
|
|
|
|
#include <boost/math/distributions.hpp>
|
|
|
|
/*`
|
|
|
|
Open up an appropriate namespace for our distributions, and
|
|
define the policy type we want. Any policies we don't
|
|
specify here will inherit the defaults:
|
|
|
|
*/
|
|
|
|
namespace my_distributions{
|
|
|
|
using namespace boost::math::policies;
|
|
|
|
typedef policy<
|
|
// return infinity and set errno rather than throw:
|
|
overflow_error<errno_on_error>,
|
|
// Don't promote double -> long double internally:
|
|
promote_double<false>,
|
|
// Return the closest integer result for discrete quantiles:
|
|
discrete_quantile<integer_round_nearest>
|
|
> my_policy;
|
|
|
|
/*`
|
|
|
|
All we need do now is invoke the BOOST_MATH_DECLARE_DISTRIBUTIONS
|
|
macro passing the floating point and policy types as arguments:
|
|
|
|
*/
|
|
|
|
BOOST_MATH_DECLARE_DISTRIBUTIONS(double, my_policy)
|
|
|
|
} // close namespace my_namespace
|
|
|
|
/*`
|
|
|
|
We now have a set of typedefs defined in namespace my_namespace
|
|
that all look something like this:
|
|
|
|
``
|
|
typedef boost::math::normal_distribution<double, my_policy> normal;
|
|
typedef boost::math::cauchy_distribution<double, my_policy> cauchy;
|
|
typedef boost::math::gamma_distribution<double, my_policy> gamma;
|
|
// etc
|
|
``
|
|
|
|
So that when we use my_namespace::normal we really end up using
|
|
`boost::math::normal_distribution<double, my_policy>`:
|
|
|
|
*/
|
|
|
|
|
|
int main()
|
|
{
|
|
//
|
|
// Start with something we know will overflow:
|
|
//
|
|
my_distributions::normal norm(10, 2);
|
|
errno = 0;
|
|
std::cout << "Result of quantile(norm, 0) is: "
|
|
<< quantile(norm, 0) << std::endl;
|
|
std::cout << "errno = " << errno << std::endl;
|
|
errno = 0;
|
|
std::cout << "Result of quantile(norm, 1) is: "
|
|
<< quantile(norm, 1) << std::endl;
|
|
std::cout << "errno = " << errno << std::endl;
|
|
//
|
|
// Now try a discrete distribution:
|
|
//
|
|
my_distributions::binomial binom(20, 0.25);
|
|
std::cout << "Result of quantile(binom, 0.05) is: "
|
|
<< quantile(binom, 0.05) << std::endl;
|
|
std::cout << "Result of quantile(complement(binom, 0.05)) is: "
|
|
<< quantile(complement(binom, 0.05)) << std::endl;
|
|
}
|
|
|
|
/*`
|
|
|
|
Which outputs:
|
|
|
|
[pre
|
|
Result of quantile(norm, 0) is: -1.#INF
|
|
errno = 34
|
|
Result of quantile(norm, 1) is: 1.#INF
|
|
errno = 34
|
|
Result of quantile(binom, 0.05) is: 1
|
|
Result of quantile(complement(binom, 0.05)) is: 8
|
|
]
|
|
|
|
This mechanism is particularly useful when we want to define a
|
|
project-wide policy, and don't want to modify the Boost source
|
|
or set - possibly fragile and easy to forget - project wide
|
|
build macros.
|
|
|
|
*/ //] ends quickbook imported section
|
|
|