contrib/libc++/include/experimental/algorithm

   1 // -*- C++ -*-
   2 //===-------------------------- algorithm ---------------------------------===//
   3 //
   4 //                     The LLVM Compiler Infrastructure
   5 //
   6 // This file is dual licensed under the MIT and the University of Illinois Open
   7 // Source Licenses. See LICENSE.TXT for details.
   8 //
   9 //===----------------------------------------------------------------------===//
  10
  11 #ifndef _LIBCPP_EXPERIMENTAL_ALGORITHM
  12 #define _LIBCPP_EXPERIMENTAL_ALGORITHM
  13
  14 /*
  15    experimental/algorithm synopsis
  16
  17 #include <algorithm>
  18
  19 namespace std {
  20 namespace experimental {
  21 inline namespace fundamentals_v1 {
  22
  23 template <class ForwardIterator, class Searcher>
  24 ForwardIterator search(ForwardIterator first, ForwardIterator last,
  25                        const Searcher &searcher);
  26 template <class PopulationIterator, class SampleIterator, class Distance,
  27           class UniformRandomNumberGenerator>
  28 SampleIterator sample(PopulationIterator first, PopulationIterator last,
  29                       SampleIterator out, Distance n,
  30                       UniformRandomNumberGenerator &&g);
  31
  32 } // namespace fundamentals_v1
  33 } // namespace experimental
  34 } // namespace std
  35
  36 */
  37
  38 #include <experimental/__config>
  39 #include <algorithm>
  40 #include <type_traits>
  41
  42 #include <__undef_min_max>
  43
  44 #include <__debug>
  45
  46 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  47 #pragma GCC system_header
  48 #endif
  49
  50 _LIBCPP_BEGIN_NAMESPACE_LFTS
  51
  52
  53 template <class _ForwardIterator, class _Searcher>
  54 _LIBCPP_INLINE_VISIBILITY
  55 _ForwardIterator search(_ForwardIterator __f, _ForwardIterator __l, const _Searcher &__s)
  56 { return __s(__f, __l); }
  57
  58
  59 template <class _PopulationIterator, class _SampleIterator, class _Distance,
  60           class _UniformRandomNumberGenerator>
  61 _LIBCPP_INLINE_VISIBILITY
  62 _SampleIterator __sample(_PopulationIterator __first,
  63                          _PopulationIterator __last, _SampleIterator __out,
  64                          _Distance __n,
  65                          _UniformRandomNumberGenerator &&__g,
  66                          input_iterator_tag) {
  67
  68   _Distance __k = 0;
  69   for (; __first != __last && __k < __n; ++__first, (void)++__k)
  70     __out[__k] = *__first;
  71   _Distance __sz = __k;
  72   for (; __first != __last; ++__first, (void)++__k) {
  73     _Distance __r = _VSTD::uniform_int_distribution<_Distance>(0, __k)(__g);
  74     if (__r < __sz)
  75       __out[__r] = *__first;
  76   }
  77   return __out + _VSTD::min(__n, __k);
  78 }
  79
  80 template <class _PopulationIterator, class _SampleIterator, class _Distance,
  81           class _UniformRandomNumberGenerator>
  82 _LIBCPP_INLINE_VISIBILITY
  83 _SampleIterator __sample(_PopulationIterator __first,
  84                          _PopulationIterator __last, _SampleIterator __out,
  85                          _Distance __n,
  86                          _UniformRandomNumberGenerator &&__g,
  87                          forward_iterator_tag) {
  88   _Distance __unsampled_sz = _VSTD::distance(__first, __last);
  89   for (__n = _VSTD::min(__n, __unsampled_sz); __n != 0; ++__first) {
  90     _Distance __r =
  91         _VSTD::uniform_int_distribution<_Distance>(0, --__unsampled_sz)(__g);
  92     if (__r < __n) {
  93       *__out++ = *__first;
  94       --__n;
  95     }
  96   }
  97   return __out;
  98 }
  99
 100 template <class _PopulationIterator, class _SampleIterator, class _Distance,
 101           class _UniformRandomNumberGenerator>
 102 _LIBCPP_INLINE_VISIBILITY
 103 _SampleIterator sample(_PopulationIterator __first,
 104                          _PopulationIterator __last, _SampleIterator __out,
 105                          _Distance __n, _UniformRandomNumberGenerator &&__g) {
 106   typedef typename iterator_traits<_PopulationIterator>::iterator_category
 107         _PopCategory;
 108   typedef typename iterator_traits<_PopulationIterator>::difference_type
 109         _Difference;
 110   typedef typename common_type<_Distance, _Difference>::type _CommonType;
 111   _LIBCPP_ASSERT(__n >= 0, "N must be a positive number.");
 112   return _VSTD_LFTS::__sample(
 113       __first, __last, __out, _CommonType(__n),
 114       _VSTD::forward<_UniformRandomNumberGenerator>(__g),
 115       _PopCategory());
 116 }
 117
 118 _LIBCPP_END_NAMESPACE_LFTS
 119
 120 #endif /* _LIBCPP_EXPERIMENTAL_ALGORITHM */