random.hpp

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/*
    The Extended Integer (XInt) Library
    A fast, portable C++ library for multi-precision integer math
    Copyright 2010 by Chad Nelson

    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/libs/xint for library home page.
*/

#ifndef BOOST_INCLUDED_XINT_RANDOM_HPP
#define BOOST_INCLUDED_XINT_RANDOM_HPP

#include <ctime>
#include <boost/random/uniform_int.hpp>
#include <boost/random/variate_generator.hpp>
#include <boost/random/mersenne_twister.hpp>

namespace boost {
namespace xint {

namespace detail {

    // This is a template only so that the static member variables don't cause
    // problems in header-only mode.
    template <typename T = void>
    class strong_random_generator_t {
        public:
        typedef unsigned int result_type;

        strong_random_generator_t();
        ~strong_random_generator_t();
        result_type operator()();

        static const bool has_fixed_range;
        static const result_type min_value;
        static const result_type max_value;
        result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const;
        result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const;
        double entropy() const;

        private:
        struct impl_t;
        impl_t *impl;
    };

    struct base_random_generator {
        typedef unsigned int result_type;
        virtual result_type operator()()=0;
        virtual ~base_random_generator() { }
    };

    template <class T>
    struct random_generator: public base_random_generator {
        typedef boost::uniform_int<result_type> dist_t;
        typedef boost::variate_generator<T&, dist_t> gen_t;
        random_generator(T& g): gen(g,
            dist_t((std::numeric_limits<result_type>::min)(),
                (std::numeric_limits<result_type>::max)())) { }
        result_type operator()() { return gen(); }
        gen_t gen;
    };

} // namespace detail

class default_random_generator: public boost::mt19937 {
    public:
    default_random_generator(): mt19937(boost::uint32_t(time(0)+clock())) { }
};

typedef detail::strong_random_generator_t<> strong_random_generator;

} // namespace xint
} // namespace boost

#endif // BOOST_INCLUDED_XINT_RANDOM_HPP