Std::make_from_tuple (3) Linux Manual Page

std::make_from_tuple – std::make_from_tuple

Synopsis

Defined in header <tuple>

template <class T, class Tuple>          (since C++17)

constexpr T make_from_tuple(Tuple&& t);

Construct an object of type T, using the elements of the tuple t as the arguments to the constructor.

Parameters

t – tuple whose elements to be used as arguments to the constructor of T

Return value

The constructed T object.

Notes

The tuple need not be std::tuple, and instead may be anything that supports std::get and std::tuple_size; in particular, std::array and std::pair may be used.
Due to guaranteed_copy_elision, T need not be movable.

Possible implementation

  namespace detail {
  template <class T, class Tuple, std::size_t… I>
  constexpr T make_from_tuple_impl( Tuple&& t, std::index_sequence<I…> )
  {
    return T(std::get<I>(std::forward<Tuple>(t))…);
  }
  } // namespace detail

  template <class T, class Tuple>
  constexpr T make_from_tuple( Tuple&& t )
  {
      return detail::make_from_tuple_impl<T>(std::forward<Tuple>(t),
          std::make_index_sequence<std::tuple_size_v<std::remove_reference_t<Tuple>>>{});
  }

Example

// Run this code

#include <iostream>

#include <tuple>
struct Foo {
    Foo(int first, float second, int third)
    {
        std::cout << first << ", " << second << ", " << third << "\n";
    }
};
int main()

{
    auto tuple = std::make_tuple(42, 3.14f, 0);
    std::make_from_tuple<Foo>(std::move(tuple));
}

Output:

42, 3.14, 0

std::make_from_tuple (3) Linux Manual Page