std::make_from_tuple
Defined in header <tuple>
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template <class T, class Tuple> constexpr T make_from_tuple(Tuple&& t); |
(since C++17) | |
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
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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
See also
creates a tuple object of the type defined by the argument types (function template) | |
creates a tuple of rvalue references (function template) | |
(C++17) |
calls a function with a tuple of arguments (function template) |