Defined in header <tuple> | ||
|---|---|---|
template< class... Tuples > std::tuple<CTypes...> tuple_cat(Tuples&&... args); | (since C++11) (constexpr since C++14) |
Constructs a tuple that is a concatenation of all tuples in args.
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.
| args | - | zero or more tuples to concatenate |
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.
#include <iostream>
#include <tuple>
#include <string>
// 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<N-1>(t);
}
};
template<class Tuple>
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)
|
(C++11) | creates a tuple object of the type defined by the argument types (function template) |
|
(C++11) | creates a tuple of lvalue references or unpacks a tuple into individual objects (function template) |
|
(C++11) | creates a tuple of forwarding references (function template) |
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https://en.cppreference.com/w/cpp/utility/tuple/tuple_cat