| /* boost random/bernoulli_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: bernoulli_distribution.hpp 60755 2010-03-22 00:45:06Z steven_watanabe $ |
| * |
| * Revision history |
| * 2001-02-18 moved to individual header files |
| */ |
| |
| #ifndef BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP |
| #define BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP |
| |
| #include <cassert> |
| #include <iostream> |
| #include <boost/random/detail/config.hpp> |
| |
| namespace boost { |
| |
| /** |
| * Instantiations of class template \bernoulli_distribution model a |
| * \random_distribution. Such a random distribution produces bool values |
| * distributed with probabilities P(true) = p and P(false) = 1-p. p is |
| * the parameter of the distribution. |
| */ |
| template<class RealType = double> |
| class bernoulli_distribution |
| { |
| public: |
| // In principle, this could work with both integer and floating-point |
| // types. Generating floating-point random numbers in the first |
| // place is probably more expensive, so use integer as input. |
| typedef int input_type; |
| typedef bool result_type; |
| |
| /** |
| * Constructs a \bernoulli_distribution object. |
| * p is the parameter of the distribution. |
| * |
| * Requires: 0 <= p <= 1 |
| */ |
| explicit bernoulli_distribution(const RealType& p_arg = RealType(0.5)) |
| : _p(p_arg) |
| { |
| assert(_p >= 0); |
| assert(_p <= 1); |
| } |
| |
| // compiler-generated copy ctor and assignment operator are fine |
| |
| /** |
| * Returns: The "p" parameter of the distribution. |
| */ |
| RealType p() const { return _p; } |
| /** |
| * 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 |
| * \bernoulli_distribution. |
| */ |
| template<class Engine> |
| result_type operator()(Engine& eng) |
| { |
| if(_p == RealType(0)) |
| return false; |
| else |
| return RealType(eng() - (eng.min)()) <= _p * RealType((eng.max)()-(eng.min)()); |
| } |
| |
| #ifndef BOOST_RANDOM_NO_STREAM_OPERATORS |
| /** |
| * Writes the parameters of the distribution to a @c std::ostream. |
| */ |
| template<class CharT, class Traits> |
| friend std::basic_ostream<CharT,Traits>& |
| operator<<(std::basic_ostream<CharT,Traits>& os, const bernoulli_distribution& bd) |
| { |
| os << bd._p; |
| return os; |
| } |
| |
| /** |
| * Reads the parameters of the distribution from a @c std::istream. |
| */ |
| template<class CharT, class Traits> |
| friend std::basic_istream<CharT,Traits>& |
| operator>>(std::basic_istream<CharT,Traits>& is, bernoulli_distribution& bd) |
| { |
| is >> std::ws >> bd._p; |
| return is; |
| } |
| #endif |
| |
| private: |
| RealType _p; |
| }; |
| |
| } // namespace boost |
| |
| #endif // BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP |