ceph/src/boost/boost/algorithm/cxx17/reduce.hpp

   1 /*
   2    Copyright (c) Marshall Clow 2017.
   3
   4    Distributed under the Boost Software License, Version 1.0. (See accompanying
   5    file LICENSE10.txt or copy at http://www.boost.org/LICENSE10.txt)
   6 */
   7
   8 /// \file  reduce.hpp
   9 /// \brief Combine the elements of a sequence into a single value
  10 /// \author Marshall Clow
  11
  12 #ifndef BOOST_ALGORITHM_REDUCE_HPP
  13 #define BOOST_ALGORITHM_REDUCE_HPP
  14
  15 #include <functional>     // for std::plus
  16 #include <iterator>       // for std::iterator_traits
  17
  18 #include <boost/range/begin.hpp>
  19 #include <boost/range/end.hpp>
  20 #include <boost/range/value_type.hpp>
  21
  22 namespace boost { namespace algorithm {
  23
  24 template<class InputIterator, class T, class BinaryOperation>
  25 T reduce(InputIterator first, InputIterator last, T init, BinaryOperation bOp)
  26 {
  27     ;
  28     for (; first != last; ++first)
  29         init = bOp(init, *first);
  30     return init;
  31 }
  32
  33 template<class InputIterator, class T>
  34 T reduce(InputIterator first, InputIterator last, T init)
  35 {
  36         typedef typename std::iterator_traits<InputIterator>::value_type VT;
  37     return reduce(first, last, init, std::plus<VT>());
  38 }
  39
  40 template<class InputIterator>
  41 typename std::iterator_traits<InputIterator>::value_type
  42 reduce(InputIterator first, InputIterator last)
  43 {
  44     return reduce(first, last,
  45        typename std::iterator_traits<InputIterator>::value_type());
  46 }
  47
  48 template<class Range>
  49 typename boost::range_value<Range>::type
  50 reduce(const Range &r)
  51 {
  52     return reduce(boost::begin(r), boost::end(r));
  53 }
  54
  55 //      Not sure that this won't be ambiguous (1)
  56 template<class Range, class T>
  57 T reduce(const Range &r, T init)
  58 {
  59     return reduce(boost::begin (r), boost::end (r), init);
  60 }
  61
  62
  63 //      Not sure that this won't be ambiguous (2)
  64 template<class Range, class T, class BinaryOperation>
  65 T reduce(const Range &r, T init, BinaryOperation bOp)
  66 {
  67     return reduce(boost::begin(r), boost::end(r), init, bOp);
  68 }
  69
  70 }} // namespace boost and algorithm
  71
  72 #endif // BOOST_ALGORITHM_REDUCE_HPP