std::make_tuple(3)

NAME
std::make_tuple - std::make_tuple

Synopsis
   Defined in header <tuple>
   template< class... Types > (since C++11)
   std::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 unwrap_decay_t = typename unwrap_refwrapper<typename std::decay<T>::type>::type;
   // or use std::unwrap_ref_decay_t (since C++20)
   template <class... Types>
   constexpr // since C++14
   std::tuple<unwrap_decay_t<Types>...> make_tuple(Types&&... args)
   {
       return std::tuple<unwrap_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

See also
   tie creates a tuple of lvalue references or unpacks a tuple into
   (C++11) individual objects
                    (function template)
   forward_as_tuple creates a tuple of forwarding references
   (C++11) (function template)
   tuple_cat creates a tuple by concatenating any number of tuples
   (C++11) (function template)
   apply calls a function with a tuple of arguments
   (C++17) (function template)