Std::make_tuple (3) Linux Manual Page

std::make_tuple – std::make_tuple

Synopsis

Defined in header <tuple>
template< class… Types > (since C++11)
tuple<VTypes…> make_tuple( Types&&… args ); (constexpr since C++14)
Creates a tuple object, deducing the target type from the types of arguments.
For each Ti in Types…, the corresponding type Vi in VTypes… is std::decay<Ti>::type unless application of std::decay results in std::reference_wrapper<X> for some type X, in which case the deduced type is X&.

Parameters

args – zero or more arguments to construct the tuple from

Return value

A std::tuple object containing the given values, created as if by std::tuple<VTypes…>(std::forward<Types>(t)…).

Possible implementation

  template <class T>
  struct unwrap_refwrapper
  {
      using type = T;
  };

  template <class T>
  struct unwrap_refwrapper<std::reference_wrapper<T>>
  {
      using type = T&;
  };

template <class T>
using special_decay_t = typename unwrap_refwrapper<typename std::decay<T>::type>::type;

  template <class… Types>
  auto make_tuple(Types&&… args)
  {
      return std::tuple<special_decay_t<Types>…>(std::forward<Types>(args)…);
  }

Example

// Run this code

#include <iostream>

#include <tuple>

#include <functional>
std::tuple<int, int> f() // this function returns multiple values

{
    int x = 5;
    return std::make_tuple(x, 7); // return {x,7}; in C++17
}
int main()

{
    // heterogeneous tuple construction
    int n = 1;
    auto t = std::make_tuple(10, "Test", 3.14, std::ref(n), n);
    n = 7;
    std::cout << "The value of t is "
              << "("
              << std::get<0>(t) << ", " << std::get<1>(t) << ", "
              << std::get<2>(t) << ", " << std::get<3>(t) << ", "
              << std::get<4>(t) << ")\n";
    // function returning multiple values
    int a, b;
    std::tie(a, b) = f();
    std::cout << a << " " << b << "\n";
}

Output:

The value of t is (10, Test, 3.14, 7, 1)
5 7

std::make_tuple (3) Linux Manual Page