/* 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