为什么从C ++ 11中删除了对范围访问？

pair<iterator,iterator>

template<class Iter>
struct iter_pair_range : std::pair<Iter,Iter> {
    iter_pair_range(std::pair<Iter,Iter> const& x)
    : std::pair<Iter,Iter>(x)
    {}
    Iter begin() const {return this->first;}
    Iter end()   const {return this->second;}
};

template<class Iter>
inline iter_pair_range<Iter> as_range(std::pair<Iter,Iter> const& x)
{ return iter_pair_range<Iter>(x); }

int main() {
    multimap<int,int> mm;
    ...
    for (auto& p : as_range(mm.equal_range(42))) {
       ...
    }
}

as_range

boost::make_iterator_range

begin()

end()

boost::make_iterator_range

std::pair

#include <utility>

template<class Iter>
struct range_t : public std::pair<Iter, Iter> {
    using pair_t = std::pair<Iter, Iter>;
    range_t(pair_t&& src)
    : std::pair<Iter, Iter>(std::forward<pair_t>(src))
    {}

    using std::pair<Iter, Iter>::first;
    using std::pair<Iter, Iter>::second;

    Iter begin() const { return first; }
    Iter end() const { return second; }
};

template<class Iter>
range_t<Iter> range(std::pair<Iter, Iter> p) {
    return range_t<Iter>(std::move(p));
}

template<class Iter>
range_t<Iter> range(Iter i1, Iter i2) {
    return range_t<Iter>(std::make_pair(std::move(i1), std::move(i2)));
}


// TEST: 

#include <iostream>
#include <set>
using namespace std;

int main() {

    multiset<int> mySet { 6,4,5,5,5,3,3,67,8,89,7,5,45,4,3 };

    cout << \"similar elements: \";
    for (const auto&i : range(mySet.lower_bound(5), mySet.upper_bound(10))) {
        cout << i << \",\";
    }
    cout << \"\\n\";

    int count = 0, sum = 0;
    for (const auto& i: range(mySet.equal_range(5)))
    {
        ++count;
        sum += i;
    }
    cout << \"5 appears \" << count << \" times\\n\"
    << \"the sum is \" << sum << \"\\n\";

return 0;
}