std::make_tuple
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std::tuple
make_tuple
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Defined in header
<tuple>
template< class... Types >
std::tuple <VTypes...> make_tuple( Types&&... args );
(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&.
[edit] Parameters
args
-
zero or more arguments to construct the tuple from
[edit] Return value
A std::tuple object containing the given values, created as if by std::tuple <VTypes...>(std::forward <Types>(t)...).
[edit] 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)...); }
[edit] 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