| /* boost random/geometric_distribution.hpp header file |
| * |
| * Copyright Jens Maurer 2000-2001 |
| * Copyright Steven Watanabe 2011 |
| * 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. |
| * |
| * $Id$ |
| * |
| * 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 <iosfwd> |
| #include <ios> |
| #include <boost/assert.hpp> |
| #include <boost/random/detail/config.hpp> |
| #include <boost/random/detail/operators.hpp> |
| #include <boost/random/uniform_01.hpp> |
| |
| namespace boost { |
| namespace random { |
| |
| /** |
| * 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$p(i) = p(1-p)^{i}\f$. |
| * |
| * @xmlwarning |
| * This distribution has been updated to match the C++ standard. |
| * Its behavior has changed from the original |
| * boost::geometric_distribution. A backwards compatible |
| * wrapper is provided in namespace boost. |
| * @endxmlwarning |
| */ |
| template<class IntType = int, class RealType = double> |
| class geometric_distribution |
| { |
| public: |
| typedef RealType input_type; |
| typedef IntType result_type; |
| |
| class param_type |
| { |
| public: |
| |
| typedef geometric_distribution distribution_type; |
| |
| /** Constructs the parameters with p. */ |
| explicit param_type(RealType p_arg = RealType(0.5)) |
| : _p(p_arg) |
| { |
| BOOST_ASSERT(RealType(0) < _p && _p < RealType(1)); |
| } |
| |
| /** Returns the p parameter of the distribution. */ |
| RealType p() const { return _p; } |
| |
| /** Writes the parameters to a std::ostream. */ |
| BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, param_type, parm) |
| { |
| os << parm._p; |
| return os; |
| } |
| |
| /** Reads the parameters from a std::istream. */ |
| BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, param_type, parm) |
| { |
| double p_in; |
| if(is >> p_in) { |
| if(p_in > RealType(0) && p_in < RealType(1)) { |
| parm._p = p_in; |
| } else { |
| is.setstate(std::ios_base::failbit); |
| } |
| } |
| return is; |
| } |
| |
| /** Returns true if the two sets of parameters are equal. */ |
| BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(param_type, lhs, rhs) |
| { return lhs._p == rhs._p; } |
| |
| /** Returns true if the two sets of parameters are different. */ |
| BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(param_type) |
| |
| |
| private: |
| RealType _p; |
| }; |
| |
| /** |
| * Contructs a new geometric_distribution with the paramter @c p. |
| * |
| * Requires: 0 < p < 1 |
| */ |
| explicit geometric_distribution(const RealType& p_arg = RealType(0.5)) |
| : _p(p_arg) |
| { |
| BOOST_ASSERT(RealType(0) < _p && _p < RealType(1)); |
| init(); |
| } |
| |
| /** Constructs a new geometric_distribution from its parameters. */ |
| explicit geometric_distribution(const param_type& parm) |
| : _p(parm.p()) |
| { |
| init(); |
| } |
| |
| // compiler-generated copy ctor and assignment operator are fine |
| |
| /** Returns: the distribution parameter @c p */ |
| RealType p() const { return _p; } |
| |
| /** Returns the smallest value that the distribution can produce. */ |
| IntType min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return IntType(0); } |
| |
| /** Returns the largest value that the distribution can produce. */ |
| IntType max BOOST_PREVENT_MACRO_SUBSTITUTION () const |
| { return (std::numeric_limits<IntType>::max)(); } |
| |
| /** Returns the parameters of the distribution. */ |
| param_type param() const { return param_type(_p); } |
| |
| /** Sets the parameters of the distribution. */ |
| void param(const param_type& parm) |
| { |
| _p = parm.p(); |
| init(); |
| } |
| |
| /** |
| * Effects: Subsequent uses of the distribution do not depend |
| * on values produced by any engine prior to invoking reset. |
| */ |
| void reset() { } |
| |
| /** |
| * Returns a random variate distributed according to the |
| * geometric_distribution. |
| */ |
| template<class Engine> |
| result_type operator()(Engine& eng) const |
| { |
| using std::log; |
| using std::floor; |
| RealType x = RealType(1) - boost::uniform_01<RealType>()(eng); |
| return IntType(floor(log(x) / _log_1mp)); |
| } |
| |
| /** |
| * Returns a random variate distributed according to the |
| * geometric distribution with parameters specified by param. |
| */ |
| template<class Engine> |
| result_type operator()(Engine& eng, const param_type& parm) const |
| { return geometric_distribution(parm)(eng); } |
| |
| /** Writes the distribution to a @c std::ostream. */ |
| BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, geometric_distribution, gd) |
| { |
| os << gd._p; |
| return os; |
| } |
| |
| /** Reads the distribution from a @c std::istream. */ |
| BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, geometric_distribution, gd) |
| { |
| param_type parm; |
| if(is >> parm) { |
| gd.param(parm); |
| } |
| return is; |
| } |
| |
| /** |
| * Returns true if the two distributions will produce identical |
| * sequences of values given equal generators. |
| */ |
| BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(geometric_distribution, lhs, rhs) |
| { return lhs._p == rhs._p; } |
| |
| /** |
| * Returns true if the two distributions may produce different |
| * sequences of values given equal generators. |
| */ |
| BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(geometric_distribution) |
| |
| private: |
| |
| /// \cond show_private |
| |
| void init() |
| { |
| using std::log; |
| _log_1mp = log(1 - _p); |
| } |
| |
| RealType _p; |
| RealType _log_1mp; |
| |
| /// \endcond |
| }; |
| |
| } // namespace random |
| |
| /// \cond show_deprecated |
| |
| /** |
| * Provided for backwards compatibility. This class is |
| * deprecated. It provides the old behavior of geometric_distribution |
| * with \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; |
| |
| explicit geometric_distribution(RealType p_arg = RealType(0.5)) |
| : _impl(1 - p_arg) {} |
| |
| RealType p() const { return 1 - _impl.p(); } |
| |
| void reset() {} |
| |
| template<class Engine> |
| IntType operator()(Engine& eng) const { return _impl(eng) + IntType(1); } |
| |
| BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, geometric_distribution, gd) |
| { |
| os << gd.p(); |
| return os; |
| } |
| |
| BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, geometric_distribution, gd) |
| { |
| RealType val; |
| if(is >> val) { |
| typename impl_type::param_type impl_param(1 - val); |
| gd._impl.param(impl_param); |
| } |
| return is; |
| } |
| |
| private: |
| typedef random::geometric_distribution<IntType, RealType> impl_type; |
| impl_type _impl; |
| }; |
| |
| /// \endcond |
| |
| } // namespace boost |
| |
| #endif // BOOST_RANDOM_GEOMETRIC_DISTRIBUTION_HPP |