Get type from a templated range

I'm trying to implement a wrapper around std::accumulate algorithm, so that instead of typing this:

std::accumulate(v.begin(), v.end(), 0, [](int x, int y) { return x * y; });

user can simply write this:

my::accumulate(v, [](int x, int y) { return x * y; });

So basically, my::accumulate, given an entity and an operation, is intended to call std::accumulate with the following arguments:

1. std::begin() from the given entity


2. std::end() from the given entity


3. default-constructed value as a starting point


4. given operation

I use free begin and end functions to allow function work on built-in arrays. The passed entity is thus a range. Here is my implementation:

template<class R, typename F>
auto accumulate(const R& r, F&& f) -> 
  typename std::iterator_traits<decltype(std::begin(r))>::value_type
{
  using T = std::iterator_traits<decltype(std::begin(r))>::value_type;
  return std::accumulate(std::begin(r), std::end(r), T{}, std::forward<F>(f));
}

It works fine. The only thing that bothers me is that ugly std::iterator_traits<decltype(std::begin(r))>::value_type construction. Is there a better way to get the type from the range?

Please note, that I'm using Visual Studio 2013, so I can use most of C++11 and some of C++14.

PS. Any other comments on the implementation? Are there any drawbacks or implications?