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partition.hpp
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1 // Range v3 library
3 //
4 // Copyright Eric Niebler 2014-present
5 //
6 // Use, modification and distribution is subject to the
7 // Boost Software License, Version 1.0. (See accompanying
8 // file LICENSE_1_0.txt or copy at
9 // http://www.boost.org/LICENSE_1_0.txt)
10 //
11 // Project home: https://github.com/ericniebler/range-v3
12 //
13 //===-------------------------- algorithm ---------------------------------===//
14 //
15 // The LLVM Compiler Infrastructure
16 //
17 // This file is dual licensed under the MIT and the University of Illinois Open
18 // Source Licenses. See LICENSE.TXT for details.
19 //
20 //===----------------------------------------------------------------------===//
21 #ifndef RANGES_V3_ALGORITHM_PARTITION_HPP
22 #define RANGES_V3_ALGORITHM_PARTITION_HPP
23 
24 #include <meta/meta.hpp>
25 
26 #include <range/v3/range_fwd.hpp>
27 
37 #include <range/v3/utility/static_const.hpp>
39 
40 #include <range/v3/detail/prologue.hpp>
41 
42 namespace ranges
43 {
46 
48  namespace detail
49  {
50  template<typename I, typename S, typename C, typename P>
51  constexpr I partition_impl(I first, S last, C pred, P proj, std::forward_iterator_tag)
52  {
53  while(true)
54  {
55  if(first == last)
56  return first;
57  if(!invoke(pred, invoke(proj, *first)))
58  break;
59  ++first;
60  }
61  for(I p = first; ++p != last;)
62  {
63  if(invoke(pred, invoke(proj, *p)))
64  {
65  ranges::iter_swap(first, p);
66  ++first;
67  }
68  }
69  return first;
70  }
71 
72  template<typename I, typename S, typename C, typename P>
73  constexpr I partition_impl(I first, S end_, C pred, P proj, std::bidirectional_iterator_tag)
74  {
75  I last = ranges::next(first, end_);
76  while(true)
77  {
78  while(true)
79  {
80  if(first == last)
81  return first;
82  if(!invoke(pred, invoke(proj, *first)))
83  break;
84  ++first;
85  }
86  do
87  {
88  if(first == --last)
89  return first;
90  } while(!invoke(pred, invoke(proj, *last)));
91  ranges::iter_swap(first, last);
92  ++first;
93  }
94  }
95  } // namespace detail
97 
98  RANGES_FUNC_BEGIN(partition)
99 
100 
101  template(typename I, typename S, typename C, typename P = identity)(
102  requires permutable<I> AND sentinel_for<S, I> AND
103  indirect_unary_predicate<C, projected<I, P>>)
104  constexpr I RANGES_FUNC(partition)(I first, S last, C pred, P proj = P{})
105  {
106  return detail::partition_impl(std::move(first),
107  std::move(last),
108  std::move(pred),
109  std::move(proj),
110  iterator_tag_of<I>());
111  }
112 
114  template(typename Rng, typename C, typename P = identity)(
115  requires forward_range<Rng> AND permutable<iterator_t<Rng>> AND
116  indirect_unary_predicate<C, projected<iterator_t<Rng>, P>>)
117  constexpr borrowed_iterator_t<Rng> RANGES_FUNC(partition)(Rng && rng, C pred, P proj = P{})
118  {
119  return detail::partition_impl(begin(rng),
120  end(rng),
121  std::move(pred),
122  std::move(proj),
123  iterator_tag_of<iterator_t<Rng>>());
124  }
125 
126  RANGES_FUNC_END(partition)
127 
128  namespace cpp20
129  {
130  using ranges::partition;
131  }
133 } // namespace ranges
134 
135 #include <range/v3/detail/epilogue.hpp>
136 
137 #endif
CPP_concept permutable
\concept permutable
Definition: concepts.hpp:840
CPP_concept indirect_unary_predicate
\concept indirect_unary_predicate
Definition: concepts.hpp:632
typename Fn::template invoke< Args... > invoke
Evaluate the invocable Fn with the arguments Args.
Definition: meta.hpp:541
front< Pair > first
Retrieve the first element of the pair Pair.
Definition: meta.hpp:2251
Tiny meta-programming library.