242 lines
7.8 KiB
Plaintext
242 lines
7.8 KiB
Plaintext
/* boost random/uniform_real_distribution.hpp header file
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*
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* Copyright Jens Maurer 2000-2001
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* Copyright Steven Watanabe 2011
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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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* $Id$
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*
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*/
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#ifndef BOOST_RANDOM_UNIFORM_REAL_DISTRIBUTION_HPP
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#define BOOST_RANDOM_UNIFORM_REAL_DISTRIBUTION_HPP
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#include <iosfwd>
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#include <ios>
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#include <istream>
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#include <boost/assert.hpp>
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#include <boost/config.hpp>
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#include <boost/random/detail/config.hpp>
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#include <boost/random/detail/operators.hpp>
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#include <boost/random/detail/signed_unsigned_tools.hpp>
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#include <boost/type_traits/is_integral.hpp>
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#include <boost/mpl/bool.hpp>
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namespace boost {
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namespace random {
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namespace detail {
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template<class Engine, class T>
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T generate_uniform_real(
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Engine& eng, T min_value, T max_value,
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boost::mpl::false_ /** is_integral<Engine::result_type> */)
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{
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for(;;) {
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typedef T result_type;
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result_type numerator = static_cast<T>(eng() - (eng.min)());
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result_type divisor = static_cast<T>((eng.max)() - (eng.min)());
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BOOST_ASSERT(divisor > 0);
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BOOST_ASSERT(numerator >= 0 && numerator <= divisor);
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T result = numerator / divisor * (max_value - min_value) + min_value;
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if(result < max_value) return result;
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}
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}
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template<class Engine, class T>
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T generate_uniform_real(
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Engine& eng, T min_value, T max_value,
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boost::mpl::true_ /** is_integral<Engine::result_type> */)
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{
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for(;;) {
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typedef T result_type;
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typedef typename Engine::result_type base_result;
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result_type numerator = static_cast<T>(subtract<base_result>()(eng(), (eng.min)()));
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result_type divisor = static_cast<T>(subtract<base_result>()((eng.max)(), (eng.min)())) + 1;
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BOOST_ASSERT(divisor > 0);
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BOOST_ASSERT(numerator >= 0 && numerator <= divisor);
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T result = numerator / divisor * (max_value - min_value) + min_value;
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if(result < max_value) return result;
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}
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}
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template<class Engine, class T>
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inline T generate_uniform_real(Engine& eng, T min_value, T max_value)
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{
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if(max_value / 2 - min_value / 2 > (std::numeric_limits<T>::max)() / 2)
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return 2 * generate_uniform_real(eng, T(min_value / 2), T(max_value / 2));
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typedef typename Engine::result_type base_result;
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return generate_uniform_real(eng, min_value, max_value,
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boost::is_integral<base_result>());
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}
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}
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/**
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* The class template uniform_real_distribution models a \random_distribution.
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* On each invocation, it returns a random floating-point value uniformly
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* distributed in the range [min..max).
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*/
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template<class RealType = double>
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class uniform_real_distribution
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{
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public:
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typedef RealType input_type;
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typedef RealType result_type;
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class param_type
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{
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public:
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typedef uniform_real_distribution distribution_type;
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/**
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* Constructs the parameters of a uniform_real_distribution.
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*
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* Requires min <= max
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*/
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explicit param_type(RealType min_arg = RealType(0.0),
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RealType max_arg = RealType(1.0))
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: _min(min_arg), _max(max_arg)
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{
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BOOST_ASSERT(_min < _max);
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}
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/** Returns the minimum value of the distribution. */
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RealType a() const { return _min; }
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/** Returns the maximum value of the distribution. */
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RealType b() const { return _max; }
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/** Writes the parameters to a @c std::ostream. */
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BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, param_type, parm)
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{
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os << parm._min << " " << parm._max;
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return os;
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}
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/** Reads the parameters from a @c std::istream. */
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BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, param_type, parm)
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{
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RealType min_in, max_in;
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if(is >> min_in >> std::ws >> max_in) {
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if(min_in <= max_in) {
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parm._min = min_in;
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parm._max = max_in;
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} else {
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is.setstate(std::ios_base::failbit);
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}
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}
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return is;
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}
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/** Returns true if the two sets of parameters are equal. */
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BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(param_type, lhs, rhs)
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{ return lhs._min == rhs._min && lhs._max == rhs._max; }
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/** Returns true if the two sets of parameters are different. */
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BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(param_type)
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private:
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RealType _min;
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RealType _max;
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};
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/**
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* Constructs a uniform_real_distribution. @c min and @c max are
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* the parameters of the distribution.
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*
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* Requires: min <= max
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*/
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explicit uniform_real_distribution(
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RealType min_arg = RealType(0.0),
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RealType max_arg = RealType(1.0))
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: _min(min_arg), _max(max_arg)
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{
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BOOST_ASSERT(min_arg < max_arg);
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}
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/** Constructs a uniform_real_distribution from its parameters. */
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explicit uniform_real_distribution(const param_type& parm)
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: _min(parm.a()), _max(parm.b()) {}
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/** Returns the minimum value of the distribution */
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RealType min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _min; }
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/** Returns the maximum value of the distribution */
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RealType max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _max; }
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/** Returns the minimum value of the distribution */
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RealType a() const { return _min; }
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/** Returns the maximum value of the distribution */
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RealType b() const { return _max; }
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/** Returns the parameters of the distribution. */
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param_type param() const { return param_type(_min, _max); }
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/** Sets the parameters of the distribution. */
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void param(const param_type& parm)
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{
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_min = parm.a();
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_max = parm.b();
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}
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/**
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* Effects: Subsequent uses of the distribution do not depend
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* on values produced by any engine prior to invoking reset.
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*/
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void reset() { }
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/** Returns a value uniformly distributed in the range [min, max). */
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template<class Engine>
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result_type operator()(Engine& eng) const
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{ return detail::generate_uniform_real(eng, _min, _max); }
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/**
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* Returns a value uniformly distributed in the range
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* [param.a(), param.b()).
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*/
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template<class Engine>
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result_type operator()(Engine& eng, const param_type& parm) const
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{ return detail::generate_uniform_real(eng, parm.a(), parm.b()); }
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/** Writes the distribution to a @c std::ostream. */
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BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, uniform_real_distribution, ud)
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{
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os << ud.param();
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return os;
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}
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/** Reads the distribution from a @c std::istream. */
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BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, uniform_real_distribution, ud)
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{
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param_type parm;
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if(is >> parm) {
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ud.param(parm);
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}
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return is;
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}
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/**
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* Returns true if the two distributions will produce identical sequences
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* of values given equal generators.
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*/
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BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(uniform_real_distribution, lhs, rhs)
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{ return lhs._min == rhs._min && lhs._max == rhs._max; }
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/**
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* Returns true if the two distributions may produce different sequences
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* of values given equal generators.
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*/
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BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(uniform_real_distribution)
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private:
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RealType _min;
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RealType _max;
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};
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} // namespace random
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} // namespace boost
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#endif // BOOST_RANDOM_UNIFORM_INT_HPP
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