std::tuple

Defined in header `<tuple>`
template< class... Types > class tuple;		(since C++11)

Class template std::tuple is a fixed-size collection of heterogeneous values. It is a generalization of std::pair.

If std::is_trivially_destructible<Ti>::value is true for every Ti in Types, the destructor of std::tuple is trivial.

If a program declares an explicit or partial specialization of std::tuple, the program is ill-formed, no diagnostic required.

Template parameters

Types...

the types of the elements that the tuple stores. Empty list is supported.

Member functions

(constructor)	constructs a new `tuple` (public member function)
operator=	assigns the contents of one `tuple` to another (public member function)
swap	swaps the contents of two `tuple`s (public member function)

Non-member functions

make_tuple (C++11)	creates a `tuple` object of the type defined by the argument types (function template)
tie (C++11)	creates a `tuple` of lvalue references or unpacks a tuple into individual objects (function template)
forward_as_tuple (C++11)	creates a `tuple` of forwarding references (function template)
tuple_cat (C++11)	creates a `tuple` by concatenating any number of tuples (function template)
get(std::tuple) (C++11)	tuple accesses specified element (function template)
operator==operator!=operator<operator<=operator>operator>=operator<=> (removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(C++20)	lexicographically compares the values in the tuple (function template)
std::swap(std::tuple) (C++11)	specializes the `std::swap` algorithm (function template)

Helper concepts

tuple-likepair-like

(C++23)

specifies that a type implemented the tuple protocol
(std::get, std::tuple_element, std::tuple_size)
(exposition-only concept*)

Helper classes

std::tuple_size<std::tuple> (C++11)	obtains the size of a `tuple` (class template specialization)
std::tuple_element<std::tuple> (C++11)	obtains the type of the specified element (class template specialization)
std::uses_allocator<std::tuple> (C++11)	specializes the `std::uses_allocator` type trait (class template specialization)
std::basic_common_reference<tuple-like> (C++23)	determines the common reference type of a `tuple` and a `tuple-like` type (class template specialization)
std::common_type<tuple-like> (C++23)	determines the common type of a `tuple` and a `tuple-like` type (class template specialization)
std::formatter<std::tuple> (C++23)	formatting support for `tuple` (class template specialization)
ignore (C++11)	placeholder to skip an element when unpacking a `tuple` using `tie` (constant)

Helper specializations

template< class... Ts >
constexpr bool enable_nonlocking_formatter_optimization<std::tuple<Ts...>> 
 = (enable_nonlocking_formatter_optimization<Ts> && ...);

(since C++23)

This specialization of std::enable_nonlocking_formatter_optimization enables efficient implementation of std::print and std::println for printing a tuple object when each element type enables it.

Deduction guides (since C++17)

Notes

Until N4387 (applied as a defect report for C++11), a function could not return a tuple using copy-list-initialization:

std::tuple<int, int> foo_tuple()
{
    return {1, -1};  // Error until N4387
    return std::tuple<int, int>{1, -1}; // Always works
    return std::make_tuple(1, -1); // Always works
}

Example

#include <iostream>
#include <stdexcept>
#include <string>
#include <tuple>

std::tuple<double, char, std::string> get_student(int id)
{
    switch (id)
    {
        case 0: return {3.8, 'A', "Lisa Simpson"};
        case 1: return {2.9, 'C', "Milhouse Van Houten"};
        case 2: return {1.7, 'D', "Ralph Wiggum"};
        case 3: return {0.6, 'F', "Bart Simpson"};
    }
    
    throw std::invalid_argument("id");
}

int main()
{
    const auto student0 = get_student(0);
    std::cout << "ID: 0, "
              << "GPA: " << std::get<0>(student0) << ", "
              << "grade: " << std::get<1>(student0) << ", "
              << "name: " << std::get<2>(student0) << '\n';
    
    const auto student1 = get_student(1);
    std::cout << "ID: 1, "
              << "GPA: " << std::get<double>(student1) << ", "
              << "grade: " << std::get<char>(student1) << ", "
              << "name: " << std::get<std::string>(student1) << '\n';
    
    double gpa2;
    char grade2;
    std::string name2;
    std::tie(gpa2, grade2, name2) = get_student(2);
    std::cout << "ID: 2, "
              << "GPA: " << gpa2 << ", "
              << "grade: " << grade2 << ", "
              << "name: " << name2 << '\n';
    
    // C++17 structured binding:
    const auto [gpa3, grade3, name3] = get_student(3);
    std::cout << "ID: 3, "
              << "GPA: " << gpa3 << ", "
              << "grade: " << grade3 << ", "
              << "name: " << name3 << '\n';
}

Output:

ID: 0, GPA: 3.8, grade: A, name: Lisa Simpson
ID: 1, GPA: 2.9, grade: C, name: Milhouse Van Houten
ID: 2, GPA: 1.7, grade: D, name: Ralph Wiggum
ID: 3, GPA: 0.6, grade: F, name: Bart Simpson

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 2796	C++11	triviality of the destructor of `std::tuple` was unspecified	specified
LWG 3990	C++11	a program could declare an explicit or partial specialization of `std::tuple`	the program is ill-formed in this case (no diagnostic required)

References

C++23 standard (ISO/IEC 14882:2024):

22.4 Tuples [tuple]

C++20 standard (ISO/IEC 14882:2020):

20.5 Tuples [tuple]

C++17 standard (ISO/IEC 14882:2017):

23.5 Tuples [tuple]

C++14 standard (ISO/IEC 14882:2014):

20.4 Tuples [tuple]

C++11 standard (ISO/IEC 14882:2011):

20.4 Tuples [tuple]