/* 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,v 1.15 2004/07/27 03:43:32 dgregor Exp $

  *

  * 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 = result_type(0), 

                                result_type sigma = result_type(1))

     : _median(median), _sigma(sigma) { }

   // 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