sl@0: /* boost random/binomial_distribution.hpp header file
sl@0:  *
sl@0:  * Copyright Jens Maurer 2002
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: binomial_distribution.hpp,v 1.10 2005/06/24 22:13:43 jmaurer Exp $
sl@0:  *
sl@0:  */
sl@0: 
sl@0: #ifndef BOOST_RANDOM_BINOMIAL_DISTRIBUTION_HPP
sl@0: #define BOOST_RANDOM_BINOMIAL_DISTRIBUTION_HPP
sl@0: 
sl@0: #include <cmath>
sl@0: #include <cassert>
sl@0: #include <boost/random/bernoulli_distribution.hpp>
sl@0: 
sl@0: namespace boost {
sl@0: 
sl@0: // Knuth
sl@0: template<class IntType = int, class RealType = double>
sl@0: class binomial_distribution
sl@0: {
sl@0: public:
sl@0:   typedef typename bernoulli_distribution<RealType>::input_type input_type;
sl@0:   typedef IntType result_type;
sl@0: 
sl@0:   explicit binomial_distribution(IntType t = 1,
sl@0:                                  const RealType& p = RealType(0.5))
sl@0:     : _bernoulli(p), _t(t)
sl@0:   {
sl@0:     assert(t >= 0);
sl@0:     assert(RealType(0) <= 0 && p <= RealType(1));
sl@0:   }
sl@0: 
sl@0:   // compiler-generated copy ctor and assignment operator are fine
sl@0: 
sl@0:   IntType t() const { return _t; }
sl@0:   RealType p() const { return _bernoulli.p(); }
sl@0:   void reset() { }
sl@0: 
sl@0:   template<class Engine>
sl@0:   result_type operator()(Engine& eng)
sl@0:   {
sl@0:     // TODO: This is O(_t), but it should be O(log(_t)) for large _t
sl@0:     result_type n = 0;
sl@0:     for(IntType i = 0; i < _t; ++i)
sl@0:       if(_bernoulli(eng))
sl@0:         ++n;
sl@0:     return n;
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 binomial_distribution& bd)
sl@0:   {
sl@0:     os << bd._bernoulli << " " << bd._t;
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, binomial_distribution& bd)
sl@0:   {
sl@0:     is >> std::ws >> bd._bernoulli >> std::ws >> bd._t;
sl@0:     return is;
sl@0:   }
sl@0: #endif
sl@0: 
sl@0: private:
sl@0:   bernoulli_distribution<RealType> _bernoulli;
sl@0:   IntType _t;
sl@0: };
sl@0: 
sl@0: } // namespace boost
sl@0: 
sl@0: #endif // BOOST_RANDOM_BINOMIAL_DISTRIBUTION_HPP