Thread: trailing return from std::tuple

Hi,
I'm on C++11, is it possible from decltype to determine which type the call operator must use as return type from std::tuple? The testing code:

Code:

#include <iostream>
#include <tuple>

using namespace std;

class A
{
        tuple<string, int> data{"abc", 1};
public:
        auto operator()(size_t p) -> decltype(get<p>(data))
        {
                return get<p>(data);
        }
};

int main()
{
        A a;
        cout << a(0) << endl;
        cout << a(1) << endl;

        return EXIT_SUCCESS;
}

It doesn't compile and returns:

Code:

test.cpp:10:44: error: invalid operands of types ‘<unresolved overloaded function type>’ and ‘size_t {aka long unsigned int}’ to binary ‘operator<’
  auto operator()(size_t p) -> decltype(get<p>(data))
                                            ^
test.cpp: In function ‘int main()’:
test.cpp:19:13: error: no match for call to ‘(A) (int)’
  cout << a(0) << endl;
             ^
test.cpp:20:13: error: no match for call to ‘(A) (int)’
  cout << a(1) << endl;
             ^

But if I use get<0>(data) instead:

Code:

#include <iostream>
#include <tuple>

using namespace std;

class A
{
        tuple<string, int> data{"abc", 1};
public:
        auto operator()(size_t p) -> decltype(get<0>(data))
        {                               //        ^ - - - - - - size_t literal
                return get<0>(data);
        }               // ^ - - - - - - size_t literal
};

int main()
{
        A a;
        cout << a(0) << endl;
        cout << a(1) << endl;

        return EXIT_SUCCESS;
}

It compiles and returns:

Code:

test.cpp:10:25: warning: unused parameter ‘p’ [-Wunused-parameter]
  auto operator()(size_t p) -> decltype(get<0>(data))
                         ^
abc
abc

Is there a way to have that code running using the size_t p argument?
Thanks in advance for any answer, best regards
Franco