/* boost random/binomial_distribution.hpp header file

  *

  * Copyright Jens Maurer 2002

  * 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: binomial_distribution.hpp,v 1.10 2005/06/24 22:13:43 jmaurer Exp $

  *

  */

 #ifndef BOOST_RANDOM_BINOMIAL_DISTRIBUTION_HPP

 #define BOOST_RANDOM_BINOMIAL_DISTRIBUTION_HPP

 #include <cmath>

 #include <cassert>

 #include <boost/random/bernoulli_distribution.hpp>

 namespace boost {

 // Knuth

 template<class IntType = int, class RealType = double>

 class binomial_distribution

 {

 public:

   typedef typename bernoulli_distribution<RealType>::input_type input_type;

   typedef IntType result_type;

   explicit binomial_distribution(IntType t = 1,

                                  const RealType& p = RealType(0.5))

     : _bernoulli(p), _t(t)

   {

     assert(t >= 0);

     assert(RealType(0) <= 0 && p <= RealType(1));

   }

   // compiler-generated copy ctor and assignment operator are fine

   IntType t() const { return _t; }

   RealType p() const { return _bernoulli.p(); }

   void reset() { }

   template<class Engine>

   result_type operator()(Engine& eng)

   {

     // TODO: This is O(_t), but it should be O(log(_t)) for large _t

     result_type n = 0;

     for(IntType i = 0; i < _t; ++i)

       if(_bernoulli(eng))

         ++n;

     return n;

   }

 #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 binomial_distribution& bd)

   {

     os << bd._bernoulli << " " << bd._t;

     return os;

   }

   template<class CharT, class Traits>

   friend std::basic_istream<CharT,Traits>&

   operator>>(std::basic_istream<CharT,Traits>& is, binomial_distribution& bd)

   {

     is >> std::ws >> bd._bernoulli >> std::ws >> bd._t;

     return is;

   }

 #endif

 private:

   bernoulli_distribution<RealType> _bernoulli;

   IntType _t;

 };

 } // namespace boost

 #endif // BOOST_RANDOM_BINOMIAL_DISTRIBUTION_HPP