std::tuple_cat - cppreference.com (original) (raw)
| Defined in header | | | | ---------------------------------------------------------------------------------------------------------------------------- | | --------------------------- | | template< class... Tuples > std::tuple</* CTypes */...> tuple_cat( Tuples&&... args ); | | (since C++11) (until C++14) | | template< class... Tuples > constexpr std::tuple</* CTypes */...> tuple_cat( Tuples&&... args ); | | (since C++14) (until C++23) | | template< tuple-like... Tuples > constexpr std::tuple</* CTypes */...> tuple_cat( Tuples&&... args ); | | (since C++23) |
Constructs a tuple that is a concatenation of all tuples in args. The element types /* CTypes */ of the returned tuple is formed by concatenating the elements type packs of all std::tuple(until C++23)tuple-like(since C++23) types in Tuples in order.
| The behavior is undefined if any type in std::decay_t<Tuples>... is not a specialization of std::tuple. However, an implementation may choose to support types (such as std::array and std::pair) that follow the tuple-like protocol. | (until C++23) |
|---|---|
| The types std::decay_t<Tuples>... are constrained to be tuple-like, i.e. each type therein is required to be a specialization of std::tuple or another type (such as std::array and std::pair) that models tuple-like. | (since C++23) |
If any type in /* CTypes */ is not constructible from the type of the corresponding element in the sequence of elements concatenated from args, the behavior is undefined(until C++23)the program is ill-formed(since C++23).
[edit] Parameters
| args | - | zero or more tuples to concatenate |
|---|
[edit] Return value
A std::tuple object composed of all elements of all argument tuples constructed from std::get<j>(std::forward<Ti>(arg)) for each individual element.
[edit] Example
#include #include #include // helper function to print a tuple of any size template<class Tuple, std::size_t N> struct TuplePrinter { static void print(const Tuple& t) { TuplePrinter<Tuple, N - 1>::print(t); std::cout << ", " << std::get(t); } }; template struct TuplePrinter<Tuple, 1> { static void print(const Tuple& t) { std::cout << std::get<0>(t); } }; template<typename... Args, std::enable_if_t<sizeof...(Args) == 0, int> = 0> void print(const std::tuple<Args...>& t) { std::cout << "()\n"; } template<typename... Args, std::enable_if_t<sizeof...(Args) != 0, int> = 0> void print(const std::tuple<Args...>& t) { std::cout << "("; TuplePrinter<decltype(t), sizeof...(Args)>::print(t); std::cout << ")\n"; } // end helper function int main() { std::tuple<int, std::string, float> t1(10, "Test", 3.14); int n = 7; auto t2 = std::tuple_cat(t1, std::make_tuple("Foo", "bar"), t1, std::tie(n)); n = 42; print(t2); }
Output:
(10, Test, 3.14, Foo, bar, 10, Test, 3.14, 42)