sl@0: /* boost random/cauchy_distribution.hpp header file
sl@0:  *
sl@0:  * Copyright Jens Maurer 2000-2001
sl@0:  * Distributed under the Boost Software License, Version 1.0. (See
sl@0:  * accompanying file LICENSE_1_0.txt or copy at
sl@0:  * http://www.boost.org/LICENSE_1_0.txt)
sl@0:  *
sl@0:  * See http://www.boost.org for most recent version including documentation.
sl@0:  *
sl@0:  * $Id: cauchy_distribution.hpp,v 1.15 2004/07/27 03:43:32 dgregor Exp $
sl@0:  *
sl@0:  * Revision history
sl@0:  *  2001-02-18  moved to individual header files
sl@0:  */
sl@0: 
sl@0: #ifndef BOOST_RANDOM_CAUCHY_DISTRIBUTION_HPP
sl@0: #define BOOST_RANDOM_CAUCHY_DISTRIBUTION_HPP
sl@0: 
sl@0: #include <cmath>
sl@0: #include <iostream>
sl@0: #include <boost/limits.hpp>
sl@0: #include <boost/static_assert.hpp>
sl@0: 
sl@0: namespace boost {
sl@0: 
sl@0: #if defined(__GNUC__) && (__GNUC__ < 3)
sl@0: // Special gcc workaround: gcc 2.95.x ignores using-declarations
sl@0: // in template classes (confirmed by gcc author Martin v. Loewis)
sl@0:   using std::tan;
sl@0: #endif
sl@0: 
sl@0: // Cauchy distribution: p(x) = sigma/(pi*(sigma**2 + (x-median)**2))
sl@0: template<class RealType = double>
sl@0: class cauchy_distribution
sl@0: {
sl@0: public:
sl@0:   typedef RealType input_type;
sl@0:   typedef RealType result_type;
sl@0: 
sl@0: #ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
sl@0:   BOOST_STATIC_ASSERT(!std::numeric_limits<RealType>::is_integer);
sl@0: #endif
sl@0: 
sl@0:   explicit cauchy_distribution(result_type median = result_type(0), 
sl@0:                                result_type sigma = result_type(1))
sl@0:     : _median(median), _sigma(sigma) { }
sl@0: 
sl@0:   // compiler-generated copy ctor and assignment operator are fine
sl@0: 
sl@0:   result_type median() const { return _median; }
sl@0:   result_type sigma() const { return _sigma; }
sl@0:   void reset() { }
sl@0: 
sl@0:   template<class Engine>
sl@0:   result_type operator()(Engine& eng)
sl@0:   {
sl@0:     // Can we have a boost::mathconst please?
sl@0:     const result_type pi = result_type(3.14159265358979323846);
sl@0: #ifndef BOOST_NO_STDC_NAMESPACE
sl@0:     using std::tan;
sl@0: #endif
sl@0:     return _median + _sigma * tan(pi*(eng()-result_type(0.5)));
sl@0:   }
sl@0: 
sl@0: #if !defined(BOOST_NO_OPERATORS_IN_NAMESPACE) && !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
sl@0:   template<class CharT, class Traits>
sl@0:   friend std::basic_ostream<CharT,Traits>&
sl@0:   operator<<(std::basic_ostream<CharT,Traits>& os, const cauchy_distribution& cd)
sl@0:   {
sl@0:     os << cd._median << " " << cd._sigma;
sl@0:     return os;
sl@0:   }
sl@0: 
sl@0:   template<class CharT, class Traits>
sl@0:   friend std::basic_istream<CharT,Traits>&
sl@0:   operator>>(std::basic_istream<CharT,Traits>& is, cauchy_distribution& cd)
sl@0:   {
sl@0:     is >> std::ws >> cd._median >> std::ws >> cd._sigma;
sl@0:     return is;
sl@0:   }
sl@0: #endif
sl@0: 
sl@0: private:
sl@0:   result_type _median, _sigma;
sl@0: };
sl@0: 
sl@0: } // namespace boost
sl@0: 
sl@0: #endif // BOOST_RANDOM_CAUCHY_DISTRIBUTION_HPP