std:: tuple_cat

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.

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) .

Parameters

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.

Example

#include <iostream>
#include <string>
#include <tuple>
 
// 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);
}

(10, Test, 3.14, Foo, bar, 10, Test, 3.14, 42)

See also