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 <iterator> // for std::distance, advance
16
17 #include <boost/config.hpp>
18 #include <boost/range/begin.hpp>
19 #include <boost/range/end.hpp>
20
21 namespace boost { namespace algorithm {
22
23 /// \fn partition_point ( ForwardIterator first, ForwardIterator last, Predicate p )
24 /// \brief Given a partitioned range, returns the partition point, i.e, the first element
25 /// that does not satisfy p
26 ///
27 /// \param first The start of the input sequence
28 /// \param last One past the end of the input sequence
29 /// \param p The predicate to test the values with
30 /// \note This function is part of the C++2011 standard library.
31 template <typename ForwardIterator, typename Predicate>
partition_point(ForwardIterator first,ForwardIterator last,Predicate p)32 ForwardIterator partition_point ( ForwardIterator first, ForwardIterator last, Predicate p )
33 {
34 std::size_t dist = std::distance ( first, last );
35 while ( first != last ) {
36 std::size_t d2 = dist / 2;
37 ForwardIterator ret_val = first;
38 std::advance (ret_val, d2);
39 if (p (*ret_val)) {
40 first = ++ret_val;
41 dist -= d2 + 1;
42 }
43 else {
44 last = ret_val;
45 dist = d2;
46 }
47 }
48 return first;
49 }
50
51 /// \fn partition_point ( Range &r, Predicate p )
52 /// \brief Given a partitioned range, returns the partition point
53 ///
54 /// \param r The input range
55 /// \param p The predicate to test the values with
56 ///
57 template <typename Range, typename Predicate>
partition_point(Range & r,Predicate p)58 typename boost::range_iterator<Range>::type partition_point ( Range &r, Predicate p )
59 {
60 return boost::algorithm::partition_point (boost::begin(r), boost::end(r), p);
61 }
62
63
64 }}
65
66 #endif // BOOST_ALGORITHM_PARTITION_POINT_HPP
67