Import uniform_int_dist.h from gcc 7.1.0/7.2.0
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code/uniform_int_dist.h
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375
code/uniform_int_dist.h
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// Class template uniform_int_distribution -*- C++ -*-
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// Copyright (C) 2009-2017 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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/**
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* @file bits/uniform_int_dist.h
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* This is an internal header file, included by other library headers.
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* Do not attempt to use it directly. @headername{random}
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*/
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#ifndef _GLIBCXX_BITS_UNIFORM_INT_DIST_H
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#define _GLIBCXX_BITS_UNIFORM_INT_DIST_H
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#include <type_traits>
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#include <limits>
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namespace std _GLIBCXX_VISIBILITY(default)
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{
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namespace __detail
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{
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_GLIBCXX_BEGIN_NAMESPACE_VERSION
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/* Determine whether number is a power of 2. */
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template<typename _Tp>
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inline bool
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_Power_of_2(_Tp __x)
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{
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return ((__x - 1) & __x) == 0;
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};
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_GLIBCXX_END_NAMESPACE_VERSION
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}
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_GLIBCXX_BEGIN_NAMESPACE_VERSION
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/**
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* @brief Uniform discrete distribution for random numbers.
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* A discrete random distribution on the range @f$[min, max]@f$ with equal
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* probability throughout the range.
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*/
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template<typename _IntType = int>
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class uniform_int_distribution
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{
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static_assert(std::is_integral<_IntType>::value,
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"template argument must be an integral type");
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public:
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/** The type of the range of the distribution. */
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typedef _IntType result_type;
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/** Parameter type. */
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struct param_type
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{
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typedef uniform_int_distribution<_IntType> distribution_type;
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explicit
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param_type(_IntType __a = 0,
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_IntType __b = std::numeric_limits<_IntType>::max())
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: _M_a(__a), _M_b(__b)
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{
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__glibcxx_assert(_M_a <= _M_b);
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}
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result_type
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a() const
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{ return _M_a; }
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result_type
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b() const
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{ return _M_b; }
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friend bool
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operator==(const param_type& __p1, const param_type& __p2)
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{ return __p1._M_a == __p2._M_a && __p1._M_b == __p2._M_b; }
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friend bool
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operator!=(const param_type& __p1, const param_type& __p2)
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{ return !(__p1 == __p2); }
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private:
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_IntType _M_a;
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_IntType _M_b;
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};
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public:
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/**
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* @brief Constructs a uniform distribution object.
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*/
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explicit
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uniform_int_distribution(_IntType __a = 0,
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_IntType __b = std::numeric_limits<_IntType>::max())
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: _M_param(__a, __b)
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{ }
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explicit
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uniform_int_distribution(const param_type& __p)
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: _M_param(__p)
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{ }
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/**
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* @brief Resets the distribution state.
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*
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* Does nothing for the uniform integer distribution.
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*/
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void
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reset() { }
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result_type
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a() const
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{ return _M_param.a(); }
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result_type
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b() const
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{ return _M_param.b(); }
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/**
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* @brief Returns the parameter set of the distribution.
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*/
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param_type
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param() const
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{ return _M_param; }
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/**
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* @brief Sets the parameter set of the distribution.
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* @param __param The new parameter set of the distribution.
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*/
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void
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param(const param_type& __param)
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{ _M_param = __param; }
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/**
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* @brief Returns the inclusive lower bound of the distribution range.
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*/
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result_type
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min() const
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{ return this->a(); }
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/**
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* @brief Returns the inclusive upper bound of the distribution range.
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*/
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result_type
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max() const
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{ return this->b(); }
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/**
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* @brief Generating functions.
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*/
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template<typename _UniformRandomNumberGenerator>
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result_type
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operator()(_UniformRandomNumberGenerator& __urng)
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{ return this->operator()(__urng, _M_param); }
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template<typename _UniformRandomNumberGenerator>
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result_type
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operator()(_UniformRandomNumberGenerator& __urng,
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const param_type& __p);
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template<typename _ForwardIterator,
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typename _UniformRandomNumberGenerator>
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void
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__generate(_ForwardIterator __f, _ForwardIterator __t,
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_UniformRandomNumberGenerator& __urng)
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{ this->__generate(__f, __t, __urng, _M_param); }
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template<typename _ForwardIterator,
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typename _UniformRandomNumberGenerator>
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void
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__generate(_ForwardIterator __f, _ForwardIterator __t,
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_UniformRandomNumberGenerator& __urng,
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const param_type& __p)
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{ this->__generate_impl(__f, __t, __urng, __p); }
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template<typename _UniformRandomNumberGenerator>
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void
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__generate(result_type* __f, result_type* __t,
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_UniformRandomNumberGenerator& __urng,
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const param_type& __p)
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{ this->__generate_impl(__f, __t, __urng, __p); }
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/**
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* @brief Return true if two uniform integer distributions have
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* the same parameters.
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*/
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friend bool
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operator==(const uniform_int_distribution& __d1,
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const uniform_int_distribution& __d2)
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{ return __d1._M_param == __d2._M_param; }
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private:
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template<typename _ForwardIterator,
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typename _UniformRandomNumberGenerator>
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void
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__generate_impl(_ForwardIterator __f, _ForwardIterator __t,
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_UniformRandomNumberGenerator& __urng,
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const param_type& __p);
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param_type _M_param;
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};
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template<typename _IntType>
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template<typename _UniformRandomNumberGenerator>
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typename uniform_int_distribution<_IntType>::result_type
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uniform_int_distribution<_IntType>::
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operator()(_UniformRandomNumberGenerator& __urng,
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const param_type& __param)
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{
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typedef typename _UniformRandomNumberGenerator::result_type
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_Gresult_type;
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typedef typename std::make_unsigned<result_type>::type __utype;
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typedef typename std::common_type<_Gresult_type, __utype>::type
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__uctype;
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const __uctype __urngmin = __urng.min();
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const __uctype __urngmax = __urng.max();
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const __uctype __urngrange = __urngmax - __urngmin;
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const __uctype __urange
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= __uctype(__param.b()) - __uctype(__param.a());
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__uctype __ret;
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if (__urngrange > __urange)
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{
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// downscaling
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const __uctype __uerange = __urange + 1; // __urange can be zero
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const __uctype __scaling = __urngrange / __uerange;
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const __uctype __past = __uerange * __scaling;
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do
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__ret = __uctype(__urng()) - __urngmin;
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while (__ret >= __past);
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__ret /= __scaling;
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}
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else if (__urngrange < __urange)
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{
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// upscaling
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/*
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Note that every value in [0, urange]
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can be written uniquely as
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(urngrange + 1) * high + low
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where
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high in [0, urange / (urngrange + 1)]
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and
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low in [0, urngrange].
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*/
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__uctype __tmp; // wraparound control
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do
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{
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const __uctype __uerngrange = __urngrange + 1;
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__tmp = (__uerngrange * operator()
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(__urng, param_type(0, __urange / __uerngrange)));
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__ret = __tmp + (__uctype(__urng()) - __urngmin);
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}
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while (__ret > __urange || __ret < __tmp);
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}
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else
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__ret = __uctype(__urng()) - __urngmin;
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return __ret + __param.a();
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}
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template<typename _IntType>
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template<typename _ForwardIterator,
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typename _UniformRandomNumberGenerator>
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void
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uniform_int_distribution<_IntType>::
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__generate_impl(_ForwardIterator __f, _ForwardIterator __t,
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_UniformRandomNumberGenerator& __urng,
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const param_type& __param)
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{
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__glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
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typedef typename _UniformRandomNumberGenerator::result_type
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_Gresult_type;
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typedef typename std::make_unsigned<result_type>::type __utype;
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typedef typename std::common_type<_Gresult_type, __utype>::type
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__uctype;
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const __uctype __urngmin = __urng.min();
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const __uctype __urngmax = __urng.max();
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const __uctype __urngrange = __urngmax - __urngmin;
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const __uctype __urange
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= __uctype(__param.b()) - __uctype(__param.a());
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__uctype __ret;
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if (__urngrange > __urange)
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{
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if (__detail::_Power_of_2(__urngrange + 1)
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&& __detail::_Power_of_2(__urange + 1))
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{
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while (__f != __t)
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{
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__ret = __uctype(__urng()) - __urngmin;
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*__f++ = (__ret & __urange) + __param.a();
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}
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}
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else
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{
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// downscaling
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const __uctype __uerange = __urange + 1; // __urange can be zero
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const __uctype __scaling = __urngrange / __uerange;
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const __uctype __past = __uerange * __scaling;
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while (__f != __t)
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{
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do
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__ret = __uctype(__urng()) - __urngmin;
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while (__ret >= __past);
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*__f++ = __ret / __scaling + __param.a();
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}
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}
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}
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else if (__urngrange < __urange)
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{
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// upscaling
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/*
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Note that every value in [0, urange]
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can be written uniquely as
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(urngrange + 1) * high + low
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where
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high in [0, urange / (urngrange + 1)]
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and
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low in [0, urngrange].
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*/
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__uctype __tmp; // wraparound control
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while (__f != __t)
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{
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do
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{
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const __uctype __uerngrange = __urngrange + 1;
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__tmp = (__uerngrange * operator()
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(__urng, param_type(0, __urange / __uerngrange)));
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__ret = __tmp + (__uctype(__urng()) - __urngmin);
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}
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while (__ret > __urange || __ret < __tmp);
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*__f++ = __ret;
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}
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}
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else
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while (__f != __t)
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*__f++ = __uctype(__urng()) - __urngmin + __param.a();
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}
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// operator!= and operator<< and operator>> are defined in <bits/random.h>
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_GLIBCXX_END_NAMESPACE_VERSION
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} // namespace std
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#endif
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