1// <experimental/algorithm> -*- C++ -*-
2
3// Copyright (C) 2014-2015 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library.  This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file experimental/algorithm
26 *  This is a TS C++ Library header.
27 */
28
29#ifndef _GLIBCXX_EXPERIMENTAL_ALGORITHM
30#define _GLIBCXX_EXPERIMENTAL_ALGORITHM 1
31
32#pragma GCC system_header
33
34#if __cplusplus <= 201103L
35# include <bits/c++14_warning.h>
36#else
37
38#include <algorithm>
39#include <random>
40#include <experimental/lfts_config.h>
41
42namespace std _GLIBCXX_VISIBILITY(default)
43{
44namespace experimental
45{
46inline namespace fundamentals_v1
47{
48_GLIBCXX_BEGIN_NAMESPACE_VERSION
49
50  template<typename _ForwardIterator, typename _Searcher>
51    inline _ForwardIterator
52    search(_ForwardIterator __first, _ForwardIterator __last,
53	   const _Searcher& __searcher)
54    { return __searcher(__first, __last); }
55
56#define __cpp_lib_experimental_sample 201402
57
58  /// Reservoir sampling algorithm.
59  template<typename _InputIterator, typename _RandomAccessIterator,
60           typename _Size, typename _UniformRandomNumberGenerator>
61    _RandomAccessIterator
62    __sample(_InputIterator __first, _InputIterator __last, input_iterator_tag,
63	     _RandomAccessIterator __out, random_access_iterator_tag,
64	     _Size __n, _UniformRandomNumberGenerator&& __g)
65    {
66      using __distrib_type = std::uniform_int_distribution<_Size>;
67      using __param_type = typename __distrib_type::param_type;
68      __distrib_type __d{};
69      _Size __sample_sz = 0;
70      while (__first != __last && __sample_sz != __n)
71	{
72	  __out[__sample_sz++] = *__first;
73	  ++__first;
74	}
75      for (auto __pop_sz = __sample_sz; __first != __last;
76	  ++__first, (void)++__pop_sz)
77	{
78	  const auto __k = __d(__g, __param_type{0, __pop_sz});
79	  if (__k < __n)
80	    __out[__k] = *__first;
81	}
82      return __out + __sample_sz;
83    }
84
85  /// Selection sampling algorithm.
86  template<typename _ForwardIterator, typename _OutputIterator, typename _Cat,
87           typename _Size, typename _UniformRandomNumberGenerator>
88    _OutputIterator
89    __sample(_ForwardIterator __first, _ForwardIterator __last,
90	     forward_iterator_tag,
91	     _OutputIterator __out, _Cat,
92	     _Size __n, _UniformRandomNumberGenerator&& __g)
93    {
94      using __distrib_type = std::uniform_int_distribution<_Size>;
95      using __param_type = typename __distrib_type::param_type;
96      __distrib_type __d{};
97      _Size __unsampled_sz = std::distance(__first, __last);
98      for (__n = std::min(__n, __unsampled_sz); __n != 0; ++__first)
99	if (__d(__g, __param_type{0, --__unsampled_sz}) < __n)
100	  {
101	    *__out++ = *__first;
102	    --__n;
103	  }
104      return __out;
105    }
106
107  /// Take a random sample from a population.
108  template<typename _PopulationIterator, typename _SampleIterator,
109           typename _Distance, typename _UniformRandomNumberGenerator>
110    _SampleIterator
111    sample(_PopulationIterator __first, _PopulationIterator __last,
112	   _SampleIterator __out, _Distance __n,
113	   _UniformRandomNumberGenerator&& __g)
114    {
115      using __pop_cat = typename
116	std::iterator_traits<_PopulationIterator>::iterator_category;
117      using __samp_cat = typename
118	std::iterator_traits<_SampleIterator>::iterator_category;
119
120      static_assert(
121	  __or_<is_convertible<__pop_cat, forward_iterator_tag>,
122		is_convertible<__samp_cat, random_access_iterator_tag>>::value,
123	  "output range must use a RandomAccessIterator when input range"
124	  " does not meet the ForwardIterator requirements");
125
126      static_assert(is_integral<_Distance>::value,
127		    "sample size must be an integer type");
128
129      typename iterator_traits<_PopulationIterator>::difference_type __d = __n;
130      return std::experimental::__sample(
131	  __first, __last, __pop_cat{}, __out, __samp_cat{},
132	  __d, std::forward<_UniformRandomNumberGenerator>(__g));
133    }
134
135_GLIBCXX_END_NAMESPACE_VERSION
136} // namespace fundamentals_v1
137} // namespace experimental
138} // namespace std
139
140#endif // C++14
141
142#endif // _GLIBCXX_EXPERIMENTAL_ALGORITHM
143