C++11 variadic template based tuple sort

gistfile1.cpp

#include <iostream>
#include <utility>
#include <tuple>
using namespace std;

//
// forward declare
//

template<int N1, int N2, int LAST, typename T>
inline typename std::enable_if<N1 + 1 == LAST && N2 == LAST, void>::type
order_helper(T && t);

template<int N1, int N2, int LAST, typename T>
inline typename std::enable_if<N1 + 1 == LAST && N2 < LAST, void>::type
order_helper(T && t);

template<int N1, int N2, int LAST, typename T>
inline typename std::enable_if<N1 + 1 < LAST && N2 == LAST, void>::type
order_helper(T && t);

template<int N1, int N2, int LAST, typename T>
inline typename std::enable_if<N1 + 1 < LAST && N2 < LAST, void>::type
order_helper(T && t);


//
// N + 1 = last, N2 = last
//
template<int N1, int N2, int LAST, typename T>
inline typename std::enable_if<N1 + 1 == LAST && N2 == LAST, void>::type
order_helper(T && t)
{
    if (get<N1>(t) > get<N2>(t)) swap(get<N1>(t), get<N2>(t));
}

//
// N + 1 = last, N2 < last
//
template<int N1, int N2, int LAST, typename T>
inline typename std::enable_if<N1 + 1 == LAST && N2 < LAST, void>::type
order_helper(T && t)
{
    if (get<N1>(t) > get<N2>(t)) swap(get<N1>(t), get<N2>(t));
    order_helper<N1, N2 + 1, LAST>(t);
}


//
// N1 + 1 < last, N2 = last
//
template<int N1, int N2, int LAST, typename T>
inline typename std::enable_if<N1 + 1 < LAST && N2 == LAST, void>::type
order_helper(T && t)
{
    if (get<N1>(t) > get<N2>(t)) swap(get<N1>(t), get<N2>(t));
    order_helper<N1 + 1, N1 + 2, LAST>(t);
}


//
// N1 + 1 < last, N1 < last
//
template<int N1, int N2, int LAST, typename T>
inline typename std::enable_if<N1 + 1 < LAST && N2 < LAST, void>::type
order_helper(T && t)
{
    if (get<N1>(t) > get<N2>(t)) swap(get<N1>(t), get<N2>(t));
    order_helper<N1, N2 + 1, LAST>(t);
}


template<typename A, typename B>
tuple<A, B> order(A && a, B && b)
{
    if (a > b) return make_tuple(b, a);
    return make_tuple(a, b);
}


template<typename A, typename B, typename... Rest>
tuple<A, B, Rest...> order(A && a, B && b, Rest&&... rest)
{
    auto t = make_tuple(a, b, rest...);
    constexpr auto LAST = tuple_size<decltype(t)>::value - 1;
    order_helper<0, 1, LAST>(t);
    return t;
}


int main(int argc, const char * argv[])
{
    int a, b, c, d, e;
    tie(a, b, c, d, e) = order(4, 3, 2, 1, 8);
    
    cout << "a = " << a << '\n'
         << "b = " << b << '\n'
         << "c = " << c << '\n'
         << "d = " << d << '\n'
         << "e = " << e << '\n';
}