boost/random/cauchy_distribution.hpp
/* boost random/cauchy_distribution.hpp header file
*
* Copyright Jens Maurer 2000-2001
* Distributed under 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)
*
* See http://www.boost.org for most recent version including documentation.
*
* $Id: cauchy_distribution.hpp 41369 2007-11-25 18:07:19Z bemandawes $
*
* Revision history
* 2001-02-18 moved to individual header files
*/
#ifndef BOOST_RANDOM_CAUCHY_DISTRIBUTION_HPP
#define BOOST_RANDOM_CAUCHY_DISTRIBUTION_HPP
#include <cmath>
#include <iostream>
#include <boost/limits.hpp>
#include <boost/static_assert.hpp>
namespace boost {
#if defined(__GNUC__) && (__GNUC__ < 3)
// Special gcc workaround: gcc 2.95.x ignores using-declarations
// in template classes (confirmed by gcc author Martin v. Loewis)
using std::tan;
#endif
// Cauchy distribution: p(x) = sigma/(pi*(sigma**2 + (x-median)**2))
template<class RealType = double>
class cauchy_distribution
{
public:
typedef RealType input_type;
typedef RealType result_type;
#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
BOOST_STATIC_ASSERT(!std::numeric_limits<RealType>::is_integer);
#endif
explicit cauchy_distribution(result_type median_arg = result_type(0),
result_type sigma_arg = result_type(1))
: _median(median_arg), _sigma(sigma_arg) { }
// compiler-generated copy ctor and assignment operator are fine
result_type median() const { return _median; }
result_type sigma() const { return _sigma; }
void reset() { }
template<class Engine>
result_type operator()(Engine& eng)
{
// Can we have a boost::mathconst please?
const result_type pi = result_type(3.14159265358979323846);
#ifndef BOOST_NO_STDC_NAMESPACE
using std::tan;
#endif
return _median + _sigma * tan(pi*(eng()-result_type(0.5)));
}
#if !defined(BOOST_NO_OPERATORS_IN_NAMESPACE) && !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
template<class CharT, class Traits>
friend std::basic_ostream<CharT,Traits>&
operator<<(std::basic_ostream<CharT,Traits>& os, const cauchy_distribution& cd)
{
os << cd._median << " " << cd._sigma;
return os;
}
template<class CharT, class Traits>
friend std::basic_istream<CharT,Traits>&
operator>>(std::basic_istream<CharT,Traits>& is, cauchy_distribution& cd)
{
is >> std::ws >> cd._median >> std::ws >> cd._sigma;
return is;
}
#endif
private:
result_type _median, _sigma;
};
} // namespace boost
#endif // BOOST_RANDOM_CAUCHY_DISTRIBUTION_HPP