Thread: pair type and operator>>

What's wrong about this source code?

Code:

#include <iostream>
#include <vector>
#include <iterator>

using namespace std;

int main()
{
        pair<string, int> si;
        istream_iterator<decltype(si)> in(cin), eos;
        vector<decltype(si)> vsi;

        if(in != eos)
        {
                vsi.push_back(*in);
                ++in;
                while(in != eos)
                {
                        vsi.push_back(*in);
                        ++in;
                }
        } else  {
                cerr << "No data?!" << endl;    // no input! Warn the user
                return EXIT_FAILURE;    // indicate failure
        }

        for(const auto& p : vsi)
                cout << p.first << " " << p.second << endl;

        return EXIT_SUCCESS;
}

Error messages generated:

Code:

In file included from /usr/include/c++/4.9/iterator:66:0,
                 from test.cpp:9:
/usr/include/c++/4.9/bits/stream_iterator.h: In instantiation of ‘void std::istream_iterator<_Tp, _CharT, _Traits, _Dist>::_M_read() [with _Tp = std::pair<std::basic_string<char>, int>; _CharT = char; _Traits = std::char_traits<char>; _Dist = long int]’:
/usr/include/c++/4.9/bits/stream_iterator.h:70:17:   required from ‘std::istream_iterator<_Tp, _CharT, _Traits, _Dist>::istream_iterator(std::istream_iterator<_Tp, _CharT, _Traits, _Dist>::istream_type&) [with _Tp = std::pair<std::basic_string<char>, int>; _CharT = char; _Traits = std::char_traits<char>; _Dist = long int; std::istream_iterator<_Tp, _CharT, _Traits, _Dist>::istream_type = std::basic_istream<char>]’
test.cpp:16:39:   required from here
/usr/include/c++/4.9/bits/stream_iterator.h:121:17: error: no match for ‘operator>>’ (operand types are ‘std::istream_iterator<std::pair<std::basic_string<char>, int> >::istream_type {aka std::basic_istream<char>}’ and ‘std::pair<std::basic_string<char>, int>’)
      *_M_stream >> _M_value;
                 ^
/usr/include/c++/4.9/bits/stream_iterator.h:121:17: note: candidates are:
In file included from /usr/include/c++/4.9/iostream:40:0,
                 from test.cpp:6:
/usr/include/c++/4.9/istream:120:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__istream_type& (*)(std::basic_istream<_CharT, _Traits>::__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]
       operator>>(__istream_type& (*__pf)(__istream_type&))
       ^
/usr/include/c++/4.9/istream:120:7: note:   no known conversion for argument 1 from ‘std::pair<std::basic_string<char>, int>’ to ‘std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&) {aka std::basic_istream<char>& (*)(std::basic_istream<char>&)}’
/usr/include/c++/4.9/istream:124:7: note: std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__ios_type& (*)(std::basic_istream<_CharT, _Traits>::__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>; std::basic_istream<_CharT, _Traits>::__ios_type = std::basic_ios<char>]
       operator>>(__ios_type& (*__pf)(__ios_type&))
       ^

It looks like that the pair type has not overloaded the operator>>.
Am I right? If true, is there a rationale behind this choice? Possible workarounds? TIA
Best regards

Do you mean that way?

Code:

#include <iostream>
#include <vector>
#include <iterator>

using namespace std;

struct istream_si
{
friend  istream& operator>>(istream&, istream_si&);
friend  ostream& operator<<(ostream&, const istream_si&);
        istream_si(const string& s = string(), const int i = 0): si_pair({s, i}) { }
private:
        pair<string, int> si_pair;
};

istream& operator>>(istream& is, istream_si& item)
{
        is >> item.si_pair.first >> item.si_pair.second;
        if(!is)
                item=istream_si("", 0);
        return is;
}

ostream& operator<<(ostream& os, const istream_si& item)
{
        os      << item.si_pair.first   << " "
                << item.si_pair.second  << flush;
        return os;
}

int main()
{
        istream_si si;
        istream_iterator<decltype(si)> in(cin), eos;
        vector<decltype(si)> vsi;

        if(in != eos)
        {
                vsi.push_back(*in);
                ++in;
                while(in != eos)
                {
                        vsi.push_back(*in);
                        ++in;
                }
        } else  {
                cerr << "No data?!" << endl;    // no input! Warn the user
                return EXIT_FAILURE;    // indicate failure
        }

        for(const auto& p : vsi)
                cout << p << endl;

        return EXIT_SUCCESS;
}

I can't use template because not yet covered in the exercises series. I still don't understand why operator<< and operator>> aren't provided for pair class template, I saw that other operators (<,>,==,!=) exist since c++14 maybe they will be added in near future. Thanks again
Best regards