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/*
Copyright (c) Marshall Clow 2011-2012.
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
*/
/// \file partition_point.hpp
/// \brief Find the partition point in a sequence
/// \author Marshall Clow
#ifndef BOOST_ALGORITHM_PARTITION_POINT_HPP
#define BOOST_ALGORITHM_PARTITION_POINT_HPP
#include <algorithm> // for std::partition_point, if available
#include <boost/range/begin.hpp>
#include <boost/range/end.hpp>
namespace boost { namespace algorithm {
#if __cplusplus >= 201103L
// Use the C++11 versions of partition_point if it is available
using std::partition_point; // Section 25.3.13
#else
/// \fn partition_point ( ForwardIterator first, ForwardIterator last, Predicate p )
/// \brief Given a partitioned range, returns the partition point, i.e, the first element
/// that does not satisfy p
///
/// \param first The start of the input sequence
/// \param last One past the end of the input sequence
/// \param p The predicate to test the values with
/// \note This function is part of the C++2011 standard library.
/// We will use the standard one if it is available,
/// otherwise we have our own implementation.
template <typename ForwardIterator, typename Predicate>
ForwardIterator partition_point ( ForwardIterator first, ForwardIterator last, Predicate p )
{
std::size_t dist = std::distance ( first, last );
while ( first != last ) {
std::size_t d2 = dist / 2;
ForwardIterator ret_val = first;
std::advance (ret_val, d2);
if (p (*ret_val)) {
first = ++ret_val;
dist -= d2 + 1;
}
else {
last = ret_val;
dist = d2;
}
}
return first;
}
#endif
/// \fn partition_point ( Range &r, Predicate p )
/// \brief Given a partitioned range, returns the partition point
///
/// \param r The input range
/// \param p The predicate to test the values with
///
template <typename Range, typename Predicate>
typename boost::range_iterator<Range> partition_point ( Range &r, Predicate p )
{
return boost::algorithm::partition_point (boost::begin(r), boost::end(r), p);
}
}}
#endif // BOOST_ALGORITHM_PARTITION_POINT_HPP
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