yat  0.14.5pre
copy_k_of_n.h
1 #ifndef theplu_yat_random_copy_k_of_n
2 #define theplu_yat_random_copy_k_of_n
3 
4 // $Id: copy_k_of_n.h 3454 2015-12-09 08:29:30Z peter $
5 
6 /*
7  Copyright (C) 2015 Peter Johansson
8 
9  This file is part of the yat library, http://dev.thep.lu.se/yat
10 
11  The yat library is free software; you can redistribute it and/or
12  modify it under the terms of the GNU General Public License as
13  published by the Free Software Foundation; either version 3 of the
14  License, or (at your option) any later version.
15 
16  The yat library is distributed in the hope that it will be useful,
17  but WITHOUT ANY WARRANTY; without even the implied warranty of
18  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19  General Public License for more details.
20 
21  You should have received a copy of the GNU General Public License
22  along with yat. If not, see <http://www.gnu.org/licenses/>.
23 */
24 
25 #include "random.h"
26 
27 #include <yat/utility/yat_assert.h>
28 
29 #include <boost/concept_check.hpp>
30 #include <boost/iterator/iterator_concepts.hpp>
31 #include <boost/iterator/iterator_traits.hpp>
32 
33 namespace theplu {
34 namespace yat {
35 namespace random {
36 
56  template<typename InputIterator, typename Size1, typename Size2,
57  typename OutputIterator>
58  OutputIterator copy_k_of_n(InputIterator it, Size1 k, Size2 n,
59  OutputIterator out)
60  {
61  BOOST_CONCEPT_ASSERT((boost_concepts::ReadableIterator<InputIterator>));
62  BOOST_CONCEPT_ASSERT((boost_concepts::SinglePassIterator<InputIterator>));
63 
64  typedef typename boost::iterator_value<InputIterator>::type value_type;
65  // check that *out = *it is valid
66  BOOST_CONCEPT_ASSERT((boost_concepts::WritableIterator<OutputIterator, value_type>));
67  BOOST_CONCEPT_ASSERT((boost_concepts::IncrementableIterator<OutputIterator>));
68 
69  YAT_ASSERT( k <= n);
70 
71  DiscreteUniform rnd;
72  while (n) {
73  if (rnd(n)<k) {
74  --k;
75  *out = *it;
76  ++out;
77  }
78  --n;
79  ++it;
80  }
81  return out;
82  }
83 
84 
85 }}} // of namespace random, yat, and theplu
86 
87 #endif
OutputIterator copy_k_of_n(InputIterator it, Size1 k, Size2 n, OutputIterator out)
Definition: copy_k_of_n.h:58
Discrete uniform distribution.
Definition: random.h:400

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