/* boost random/geometric_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: geometric_distribution.hpp,v 1.16 2004/07/27 03:43:32 dgregor Exp $

  *

  * Revision history

  *  2001-02-18  moved to individual header files

  */

 #ifndef BOOST_RANDOM_GEOMETRIC_DISTRIBUTION_HPP

 #define BOOST_RANDOM_GEOMETRIC_DISTRIBUTION_HPP

 #include <cmath>          // std::log

 #include <cassert>

 #include <iostream>

 #include <boost/random/uniform_01.hpp>

 namespace boost {

 #if defined(__GNUC__) && (__GNUC__ < 3)

 // Special gcc workaround: gcc 2.95.x ignores using-declarations

 // in template classes (confirmed by gcc author Martin v. Loewis)

   using std::log;

 #endif

 // geometric distribution: p(i) = (1-p) * pow(p, i-1)   (integer)

 template<class IntType = int, class RealType = double>

 class geometric_distribution

 {

 public:

   typedef RealType input_type;

   typedef IntType result_type;

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

     : _p(p)

   {

     assert(RealType(0) < p && p < RealType(1));

     init();

   }

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

   RealType p() const { return _p; }

   void reset() { }

   template<class Engine>

   result_type operator()(Engine& eng)

   {

 #ifndef BOOST_NO_STDC_NAMESPACE

     using std::log;

     using std::floor;

 #endif

     return IntType(floor(log(RealType(1)-eng()) / _log_p)) + IntType(1);

   }

 #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 geometric_distribution& gd)

   {

     os << gd._p;

     return os;

   }

   template<class CharT, class Traits>

   friend std::basic_istream<CharT,Traits>&

   operator>>(std::basic_istream<CharT,Traits>& is, geometric_distribution& gd)

   {

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

     gd.init();

     return is;

   }

 #endif

 private:

   void init()

   {

 #ifndef BOOST_NO_STDC_NAMESPACE

     using std::log;

 #endif

     _log_p = log(_p);

   }

   RealType _p;

   RealType _log_p;

 };

 } // namespace boost

 #endif // BOOST_RANDOM_GEOMETRIC_DISTRIBUTION_HPP