/* 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