Can range based for loop work over a range

Question

If I have range (pair of 2 iterators) is there a way to write \"for each\" loop for that uses range, not a raw array or container.

Something like this:

Answer 1

As per Why was pair range access removed from C++11? you can use an adaptor e.g. the as_range at the accepted answer, boost::make_iterator_range, or write your own:

template struct range {
   It begin_, end_;
   It begin() const { return begin_; }
   It end() const { return end_; }
};
template range as_range(const std::pair &p) {
   return {p.first, p.second};
}

auto rng = std::equal_range(v.begin(),v.end(),1984);
for(const auto& elem: as_range(rng))
    ...

The reason this isn't applicable in general is that per Alastair Meredith's paper, of the algorithms,

• mismatch and partition_copy return a pair of iterators from different ranges;
• minmax returns a pair of objects that may not be iterators at all, and if they are there's no guarantee they form a range;
• minmax_element can return a range, but it can also return a reversed range (e.g. on a reverse-sorted range minmax_element will return {prev(last), first};
• equal_range is guaranteed to return a range.