sl@0: /* boost random/bernoulli_distribution.hpp header file
sl@0:  *
sl@0:  * Copyright Jens Maurer 2000-2001
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: bernoulli_distribution.hpp,v 1.19 2004/07/27 03:43:32 dgregor Exp $
sl@0:  *
sl@0:  * Revision history
sl@0:  *  2001-02-18  moved to individual header files
sl@0:  */
sl@0: 
sl@0: #ifndef BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP
sl@0: #define BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP
sl@0: 
sl@0: #include <cassert>
sl@0: #include <iostream>
sl@0: 
sl@0: namespace boost {
sl@0: 
sl@0: // Bernoulli distribution: p(true) = p, p(false) = 1-p   (boolean)
sl@0: template<class RealType = double>
sl@0: class bernoulli_distribution
sl@0: {
sl@0: public:
sl@0:   // In principle, this could work with both integer and floating-point
sl@0:   // types.  Generating floating-point random numbers in the first
sl@0:   // place is probably more expensive, so use integer as input.
sl@0:   typedef int input_type;
sl@0:   typedef bool result_type;
sl@0: 
sl@0:   explicit bernoulli_distribution(const RealType& p = RealType(0.5)) 
sl@0:     : _p(p)
sl@0:   {
sl@0:     assert(p >= 0);
sl@0:     assert(p <= 1);
sl@0:   }
sl@0: 
sl@0:   // compiler-generated copy ctor and assignment operator are fine
sl@0: 
sl@0:   RealType p() const { return _p; }
sl@0:   void reset() { }
sl@0: 
sl@0:   template<class Engine>
sl@0:   result_type operator()(Engine& eng)
sl@0:   {
sl@0:     if(_p == RealType(0))
sl@0:       return false;
sl@0:     else
sl@0:       return RealType(eng() - (eng.min)()) <= _p * RealType((eng.max)()-(eng.min)());
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 bernoulli_distribution& bd)
sl@0:   {
sl@0:     os << bd._p;
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, bernoulli_distribution& bd)
sl@0:   {
sl@0:     is >> std::ws >> bd._p;
sl@0:     return is;
sl@0:   }
sl@0: #endif
sl@0: 
sl@0: private:
sl@0:   RealType _p;
sl@0: };
sl@0: 
sl@0: } // namespace boost
sl@0: 
sl@0: #endif // BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP