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/* boost random/binomial_distribution.hpp header file
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*
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* Copyright Jens Maurer 2002
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* Distributed under the Boost Software License, Version 1.0. (See
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* accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*
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* See http://www.boost.org for most recent version including documentation.
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*
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* $Id: binomial_distribution.hpp,v 1.10 2005/06/24 22:13:43 jmaurer Exp $
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*
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*/
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#ifndef BOOST_RANDOM_BINOMIAL_DISTRIBUTION_HPP
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#define BOOST_RANDOM_BINOMIAL_DISTRIBUTION_HPP
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#include <cmath>
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#include <cassert>
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#include <boost/random/bernoulli_distribution.hpp>
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namespace boost {
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// Knuth
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template<class IntType = int, class RealType = double>
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class binomial_distribution
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{
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public:
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typedef typename bernoulli_distribution<RealType>::input_type input_type;
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typedef IntType result_type;
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explicit binomial_distribution(IntType t = 1,
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const RealType& p = RealType(0.5))
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: _bernoulli(p), _t(t)
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{
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assert(t >= 0);
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assert(RealType(0) <= 0 && p <= RealType(1));
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}
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// compiler-generated copy ctor and assignment operator are fine
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IntType t() const { return _t; }
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RealType p() const { return _bernoulli.p(); }
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void reset() { }
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template<class Engine>
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result_type operator()(Engine& eng)
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{
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// TODO: This is O(_t), but it should be O(log(_t)) for large _t
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result_type n = 0;
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for(IntType i = 0; i < _t; ++i)
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if(_bernoulli(eng))
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++n;
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return n;
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}
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#if !defined(BOOST_NO_OPERATORS_IN_NAMESPACE) && !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
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template<class CharT, class Traits>
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friend std::basic_ostream<CharT,Traits>&
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operator<<(std::basic_ostream<CharT,Traits>& os, const binomial_distribution& bd)
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{
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os << bd._bernoulli << " " << bd._t;
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return os;
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}
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template<class CharT, class Traits>
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friend std::basic_istream<CharT,Traits>&
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operator>>(std::basic_istream<CharT,Traits>& is, binomial_distribution& bd)
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{
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is >> std::ws >> bd._bernoulli >> std::ws >> bd._t;
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return is;
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}
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#endif
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private:
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bernoulli_distribution<RealType> _bernoulli;
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IntType _t;
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};
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} // namespace boost
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#endif // BOOST_RANDOM_BINOMIAL_DISTRIBUTION_HPP
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