/* boost random/bernoulli_distribution.hpp header file
 *
 * Copyright Jens Maurer 2000-2001
 * Permission to use, copy, modify, sell, and distribute this software
 * is hereby granted without fee provided that the above copyright notice
 * appears in all copies and that both that copyright notice and this
 * permission notice appear in supporting documentation,
 *
 * Jens Maurer makes no representations about the suitability of this
 * software for any purpose. It is provided "as is" without express or
 * implied warranty.
 *
 * See http://www.boost.org for most recent version including documentation.
 *
 * $Id: bernoulli_distribution.hpp,v 1.3 2001/11/14 21:53:38 jmaurer 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>

namespace boost {

// Bernoulli distribution: p(true) = p, p(false) = 1-p   (boolean)
template<class UniformRandomNumberGenerator>
class bernoulli_distribution
{
public:
  typedef UniformRandomNumberGenerator base_type;
  typedef bool result_type;
  bernoulli_distribution(base_type & rng, double p) 
    : _rng(rng),
      _threshold(static_cast<base_result>
                 (p * (_rng.max() - _rng.min())) + _rng.min())
  {
    // for p == 0, we can only set _threshold = 0, which is not enough
    assert(p > 0);
  }
  // compiler-generated copy ctor is fine
  // assignment is disallowed because there is a reference member

  result_type operator()() { return _rng() <= _threshold; }
#ifndef BOOST_NO_OPERATORS_IN_NAMESPACE
  friend bool operator==(const bernoulli_distribution& x, 
                         const bernoulli_distribution& y)
  { return x._threshold == y._threshold && x._rng == y._rng; }
#else
  // Use a member function
  bool operator==(const bernoulli_distribution& rhs) const
  { return _threshold == rhs._threshold && _rng == rhs._rng;  }
#endif
private:
  typedef typename base_type::result_type base_result;
  base_type & _rng;
  const base_result _threshold;
};

} // namespace boost

#endif // BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP
