ceph/src/boost/libs/algorithm/include/boost/algorithm/cxx11/partition_point.hpp

   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/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 template <typename ForwardIterator, typename Predicate>
  31 ForwardIterator partition_point ( ForwardIterator first, ForwardIterator last, Predicate p )
  32 {
  33     std::size_t dist = std::distance ( first, last );
  34     while ( first != last ) {
  35         std::size_t d2 = dist / 2;
  36         ForwardIterator ret_val = first;
  37         std::advance (ret_val, d2);
  38         if (p (*ret_val)) {
  39             first = ++ret_val;
  40             dist -= d2 + 1;
  41             }
  42         else {
  43             last = ret_val;
  44             dist = d2;
  45             }
  46         }
  47     return first;
  48 }
  49
  50 /// \fn partition_point ( Range &r, Predicate p )
  51 /// \brief Given a partitioned range, returns the partition point
  52 ///
  53 /// \param r        The input range
  54 /// \param p        The predicate to test the values with
  55 ///
  56 template <typename Range, typename Predicate>
  57 typename boost::range_iterator<Range>::type partition_point ( Range &r, Predicate p )
  58 {
  59     return boost::algorithm::partition_point (boost::begin(r), boost::end(r), p);
  60 }
  61
  62
  63 }}
  64
  65 #endif  // BOOST_ALGORITHM_PARTITION_POINT_HPP