/* boost random/bernoulli_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: bernoulli_distribution.hpp,v 1.19 2004/07/27 03:43:32 dgregor Exp $

 *

 * Revision history

 *  2001-02-18  moved to individual header files

 */

#ifndef BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP

#define BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP

#include <cassert>

#include <iostream>

namespace boost {

// Bernoulli distribution: p(true) = p, p(false) = 1-p   (boolean)

template<class RealType = double>

class bernoulli_distribution

{

public:

  // In principle, this could work with both integer and floating-point

  // types.  Generating floating-point random numbers in the first

  // place is probably more expensive, so use integer as input.

  typedef int input_type;

  typedef bool result_type;

  explicit bernoulli_distribution(const RealType& p = RealType(0.5)) 

    : _p(p)

  {

    assert(p >= 0);

    assert(p <= 1);

  }

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

  RealType p() const { return _p; }

  void reset() { }

  template<class Engine>

  result_type operator()(Engine& eng)

  {

    if(_p == RealType(0))

      return false;

    else

      return RealType(eng() - (eng.min)()) <= _p * RealType((eng.max)()-(eng.min)());

  }

#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 bernoulli_distribution& bd)

  {

    os << bd._p;

    return os;

  }

  template<class CharT, class Traits>

  friend std::basic_istream<CharT,Traits>&

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

  {

    is >> std::ws >> bd._p;

    return is;

  }

#endif

private:

  RealType _p;

};

} // namespace boost

#endif // BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP