| /* 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 60755 2010-03-22 00:45:06Z steven_watanabe $ |
| * |
| * Revision history |
| * 2001-02-18 moved to individual header files |
| */ |
| |
| #ifndef BOOST_RANDOM_GEOMETRIC_DISTRIBUTION_HPP |
| #define BOOST_RANDOM_GEOMETRIC_DISTRIBUTION_HPP |
| |
| #include <boost/config/no_tr1/cmath.hpp> // std::log |
| #include <cassert> |
| #include <iostream> |
| #include <boost/random/detail/config.hpp> |
| #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 |
| |
| /** |
| * An instantiation of the class template @c geometric_distribution models |
| * a \random_distribution. The distribution produces positive |
| * integers which are the number of bernoulli trials |
| * with probability @c p required to get one that fails. |
| * |
| * For the geometric distribution, \f$p(i) = (1-p) p^{i-1}\f$. |
| */ |
| template<class IntType = int, class RealType = double> |
| class geometric_distribution |
| { |
| public: |
| typedef RealType input_type; |
| typedef IntType result_type; |
| |
| /** |
| * Contructs a new geometric_distribution with the paramter @c p. |
| * |
| * Requires: 0 < p < 1 |
| */ |
| 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 |
| |
| /** |
| * Returns: the distribution parameter @c p |
| */ |
| 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); |
| } |
| |
| #ifndef BOOST_RANDOM_NO_STREAM_OPERATORS |
| 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: |
| |
| /// \cond hide_private_functions |
| |
| void init() |
| { |
| #ifndef BOOST_NO_STDC_NAMESPACE |
| using std::log; |
| #endif |
| _log_p = log(_p); |
| } |
| |
| /// \endcond |
| |
| RealType _p; |
| RealType _log_p; |
| }; |
| |
| } // namespace boost |
| |
| #endif // BOOST_RANDOM_GEOMETRIC_DISTRIBUTION_HPP |
| |