for_each_i: algorithm to iterator over a range, with an index.

gistfile1.cpp

template<class InputIterator, class Function>
Function for_each_i(InputIterator first, InputIterator last, Function f) {
  using index_type = std::iterator_traits<InputIterator>::difference_type i;
  for (index_type i {}; first!=last; ++first, ++i) {
    f(*first, i);
  }
  return std::move(f);
}

/*
25.1

add:
template<class InputIterator, class Function>
Function for_each_i(InputIterator first, InputIterator last, Function f);

25.2.4

add:

template<class InputIterator, class Function>
Function for_each_i(InputIterator first, InputIterator last, Function f);

Effects: ... for_each_i passes, as a second argument to f, an object of type iterator_traits<InputIterator>::difference_type, which is initially value initialized and incremented after each application of f.

*/