sl@0: /* boost random/geometric_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: geometric_distribution.hpp,v 1.16 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_GEOMETRIC_DISTRIBUTION_HPP
sl@0: #define BOOST_RANDOM_GEOMETRIC_DISTRIBUTION_HPP
sl@0: 
sl@0: #include <cmath>          // std::log
sl@0: #include <cassert>
sl@0: #include <iostream>
sl@0: #include <boost/random/uniform_01.hpp>
sl@0: 
sl@0: namespace boost {
sl@0: 
sl@0: #if defined(__GNUC__) && (__GNUC__ < 3)
sl@0: // Special gcc workaround: gcc 2.95.x ignores using-declarations
sl@0: // in template classes (confirmed by gcc author Martin v. Loewis)
sl@0:   using std::log;
sl@0: #endif
sl@0: 
sl@0: // geometric distribution: p(i) = (1-p) * pow(p, i-1)   (integer)
sl@0: template<class IntType = int, class RealType = double>
sl@0: class geometric_distribution
sl@0: {
sl@0: public:
sl@0:   typedef RealType input_type;
sl@0:   typedef IntType result_type;
sl@0: 
sl@0:   explicit geometric_distribution(const RealType& p = RealType(0.5))
sl@0:     : _p(p)
sl@0:   {
sl@0:     assert(RealType(0) < p && p < RealType(1));
sl@0:     init();
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: #ifndef BOOST_NO_STDC_NAMESPACE
sl@0:     using std::log;
sl@0:     using std::floor;
sl@0: #endif
sl@0:     return IntType(floor(log(RealType(1)-eng()) / _log_p)) + IntType(1);
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 geometric_distribution& gd)
sl@0:   {
sl@0:     os << gd._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, geometric_distribution& gd)
sl@0:   {
sl@0:     is >> std::ws >> gd._p;
sl@0:     gd.init();
sl@0:     return is;
sl@0:   }
sl@0: #endif
sl@0: 
sl@0: private:
sl@0:   void init()
sl@0:   {
sl@0: #ifndef BOOST_NO_STDC_NAMESPACE
sl@0:     using std::log;
sl@0: #endif
sl@0:     _log_p = log(_p);
sl@0:   }
sl@0: 
sl@0:   RealType _p;
sl@0:   RealType _log_p;
sl@0: };
sl@0: 
sl@0: } // namespace boost
sl@0: 
sl@0: #endif // BOOST_RANDOM_GEOMETRIC_DISTRIBUTION_HPP
sl@0: