std::tuple_cat

Since C++23

Header: <tuple>

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.

# Declarations

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)

# Parameters

# Return value

A std::tuple object composed of all elements of all argument tuples constructed from std::get(std::forward(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);
}

# See also