1 | /* |
2 | Copyright (c) Marshall Clow 2011-2012. |
3 | |
4 | Distributed under the Boost Software License, Version 1.0. (See accompanying |
5 | file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
6 | */ |
7 | |
8 | /// \file partition_point.hpp |
9 | /// \brief Find the partition point in a sequence |
10 | /// \author Marshall Clow |
11 | |
12 | #ifndef BOOST_ALGORITHM_PARTITION_POINT_HPP |
13 | #define BOOST_ALGORITHM_PARTITION_POINT_HPP |
14 | |
15 | #include <algorithm> // for std::partition_point, if available |
16 | |
17 | #include <boost/range/begin.hpp> |
18 | #include <boost/range/end.hpp> |
19 | |
20 | namespace boost { namespace algorithm { |
21 | |
22 | /// \fn partition_point ( ForwardIterator first, ForwardIterator last, Predicate p ) |
23 | /// \brief Given a partitioned range, returns the partition point, i.e, the first element |
24 | /// that does not satisfy p |
25 | /// |
26 | /// \param first The start of the input sequence |
27 | /// \param last One past the end of the input sequence |
28 | /// \param p The predicate to test the values with |
29 | /// \note This function is part of the C++2011 standard library. |
30 | /// We will use the standard one if it is available, |
31 | /// otherwise we have our own implementation. |
32 | template <typename ForwardIterator, typename Predicate> |
33 | ForwardIterator partition_point ( ForwardIterator first, ForwardIterator last, Predicate p ) |
34 | { |
35 | std::size_t dist = std::distance ( first, last ); |
36 | while ( first != last ) { |
37 | std::size_t d2 = dist / 2; |
38 | ForwardIterator ret_val = first; |
39 | std::advance (ret_val, d2); |
40 | if (p (*ret_val)) { |
41 | first = ++ret_val; |
42 | dist -= d2 + 1; |
43 | } |
44 | else { |
45 | last = ret_val; |
46 | dist = d2; |
47 | } |
48 | } |
49 | return first; |
50 | } |
51 | |
52 | /// \fn partition_point ( Range &r, Predicate p ) |
53 | /// \brief Given a partitioned range, returns the partition point |
54 | /// |
55 | /// \param r The input range |
56 | /// \param p The predicate to test the values with |
57 | /// |
58 | template <typename Range, typename Predicate> |
59 | typename boost::range_iterator<Range>::type partition_point ( Range &r, Predicate p ) |
60 | { |
61 | return boost::algorithm::partition_point (boost::begin(r), boost::end(r), p); |
62 | } |
63 | |
64 | |
65 | }} |
66 | |
67 | #endif // BOOST_ALGORITHM_PARTITION_POINT_HPP |
68 | |