williamr@2: /* boost random/bernoulli_distribution.hpp header file williamr@2: * williamr@2: * Copyright Jens Maurer 2000-2001 williamr@2: * Distributed under the Boost Software License, Version 1.0. (See williamr@2: * accompanying file LICENSE_1_0.txt or copy at williamr@2: * http://www.boost.org/LICENSE_1_0.txt) williamr@2: * williamr@2: * See http://www.boost.org for most recent version including documentation. williamr@2: * williamr@2: * $Id: bernoulli_distribution.hpp,v 1.19 2004/07/27 03:43:32 dgregor Exp $ williamr@2: * williamr@2: * Revision history williamr@2: * 2001-02-18 moved to individual header files williamr@2: */ williamr@2: williamr@2: #ifndef BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP williamr@2: #define BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP williamr@2: williamr@2: #include williamr@2: #include williamr@2: williamr@2: namespace boost { williamr@2: williamr@2: // Bernoulli distribution: p(true) = p, p(false) = 1-p (boolean) williamr@2: template williamr@2: class bernoulli_distribution williamr@2: { williamr@2: public: williamr@2: // In principle, this could work with both integer and floating-point williamr@2: // types. Generating floating-point random numbers in the first williamr@2: // place is probably more expensive, so use integer as input. williamr@2: typedef int input_type; williamr@2: typedef bool result_type; williamr@2: williamr@2: explicit bernoulli_distribution(const RealType& p = RealType(0.5)) williamr@2: : _p(p) williamr@2: { williamr@2: assert(p >= 0); williamr@2: assert(p <= 1); williamr@2: } williamr@2: williamr@2: // compiler-generated copy ctor and assignment operator are fine williamr@2: williamr@2: RealType p() const { return _p; } williamr@2: void reset() { } williamr@2: williamr@2: template williamr@2: result_type operator()(Engine& eng) williamr@2: { williamr@2: if(_p == RealType(0)) williamr@2: return false; williamr@2: else williamr@2: return RealType(eng() - (eng.min)()) <= _p * RealType((eng.max)()-(eng.min)()); williamr@2: } williamr@2: williamr@2: #if !defined(BOOST_NO_OPERATORS_IN_NAMESPACE) && !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS) williamr@2: template williamr@2: friend std::basic_ostream& williamr@2: operator<<(std::basic_ostream& os, const bernoulli_distribution& bd) williamr@2: { williamr@2: os << bd._p; williamr@2: return os; williamr@2: } williamr@2: williamr@2: template williamr@2: friend std::basic_istream& williamr@2: operator>>(std::basic_istream& is, bernoulli_distribution& bd) williamr@2: { williamr@2: is >> std::ws >> bd._p; williamr@2: return is; williamr@2: } williamr@2: #endif williamr@2: williamr@2: private: williamr@2: RealType _p; williamr@2: }; williamr@2: williamr@2: } // namespace boost williamr@2: williamr@2: #endif // BOOST_RANDOM_BERNOULLI_DISTRIBUTION_HPP