Standard library header <tuple> (C++11)

 

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Standard library headers

Language support
<cstddef> <cstdlib> <version> (C++20) <limits> <climits>	<cfloat> <cstdint> (C++11) <stdfloat> (C++23) <new> <typeinfo>	<source_location> (C++20) <exception> <initializer_list> (C++11) <compare> (C++20)	<coroutine> (C++20) <csignal> <csetjmp> <cstdarg>
Concepts
<concepts> (C++20)
Diagnostics
<stdexcept> <stacktrace> (C++23)	<cassert>	<cerrno>	<system_error> (C++11)
Memory management
<memory>	<memory_resource> (C++17)	<scoped_allocator> (C++11)
Metaprogramming
<type_traits> (C++11)	<ratio> (C++11)
General utilities
<utility> <tuple> (C++11) <optional> (C++17) <variant> (C++17)	<any> (C++17) <expected> (C++23) <bitset>	<functional> <typeindex> (C++11) <execution> (C++17)	<charconv> (C++17) <format> (C++20) <bit> (C++20)
Strings
<string_view> (C++17) <string>	<cctype> <cwctype>	<cstring> <cwchar>	<cuchar> (C++11)
Containers
<array> (C++11) <deque> <forward_list> (C++11) <list>	<vector> <map> <set> <unordered_map> (C++11)	<unordered_set> (C++11) <queue> <stack> <flat_map> (C++23)	<flat_set> (C++23) <span> (C++20) <mdspan> (C++23)
Iterators
<iterator>
Ranges
<ranges> (C++20)	<generator> (C++23)
Algorithms
<algorithm>	<numeric>
Numerics
<cfenv> (C++11) <complex>	<random> (C++11) <valarray>	<cmath>	<numbers> (C++20)
Time
<chrono> (C++11)	<ctime>
Localization
<locale>	<clocale>	<codecvt> (C++11/17*)
Input/output
<iosfwd> <iostream> <ios> <streambuf>	<istream> <ostream> <iomanip> <print> (C++23)	<sstream> <spanstream> (C++23) <fstream> <syncstream> (C++20)	<filesystem> (C++17) <cstdio> <cinttypes> (C++11) <strstream> (C++98*)
Regular expressions
<regex> (C++11)
Concurrency support
<stop_token> (C++20) <thread> (C++11) <atomic> (C++11)	<stdatomic.h> (C++23) <mutex> (C++11) <shared_mutex> (C++14)	<condition_variable> (C++11)   <semaphore> (C++20) <latch> (C++20)	<barrier> (C++20) <future> (C++11)
C compatibility
<cstdbool> (C++11/17/20*)   <ccomplex> (C++11/17/20*)	<ctgmath> (C++11/17/20*)	<cstdalign> (C++11/17/20*)	<ciso646> (until C++20)

 

This header is part of the general utility library.

Includes
<compare> (C++20)	Three-way comparison operator support
Classes
tuple (C++11)	implements fixed size container, which holds elements of possibly different types (class template)
tuple_size (C++11)	obtains the number of elements of a tuple-like type (class template)
tuple_element (C++11)	obtains the element types of a tuple-like type (class template)
std::tuple_size<std::tuple> (C++11)	obtains the size of tuple at compile time (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)
Constants
ignore (C++11)	placeholder to skip an element when unpacking a tuple using tie (constant)
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)
std::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)
apply (C++17)	calls a function with a tuple of arguments (function template)
make_from_tuple (C++17)	construct an object with a tuple of arguments (function template)

Synopsis

#include <compare>
 
namespace std {
  // class template tuple
  template<class... Types>
    class tuple;
 
  // tuple creation functions
  inline constexpr /* unspecified */ ignore;
 
  template<class... TTypes>
    constexpr tuple<unwrap_ref_decay_t<TTypes>...> make_tuple(TTypes&&...);
 
  template<class... TTypes>
    constexpr tuple<TTypes&&...> forward_as_tuple(TTypes&&...) noexcept;
 
  template<class... TTypes>
    constexpr tuple<TTypes&...> tie(TTypes&...) noexcept;
 
  template<class... Tuples>
    constexpr tuple<CTypes...> tuple_cat(Tuples&&...);
 
  // calling a function with a tuple of arguments
  template<class F, class Tuple>
    constexpr decltype(auto) apply(F&& f, Tuple&& t);
 
  template<class T, class Tuple>
    constexpr T make_from_tuple(Tuple&& t);
 
  // tuple helper classes
  template<class T> struct tuple_size;                  // not defined
  template<class T> struct tuple_size<const T>;
 
  template<class... Types> struct tuple_size<tuple<Types...>>;
 
  template<size_t I, class T> struct tuple_element;     // not defined
  template<size_t I, class T> struct tuple_element<I, const T>;
 
  template<size_t I, class... Types>
    struct tuple_element<I, tuple<Types...>>;
 
  template<size_t I, class T>
    using tuple_element_t = typename tuple_element<I, T>::type;
 
  // element access
  template<size_t I, class... Types>
    constexpr tuple_element_t<I, tuple<Types...>>& get(tuple<Types...>&) noexcept;
  template<size_t I, class... Types>
    constexpr tuple_element_t<I, tuple<Types...>>&& get(tuple<Types...>&&) noexcept;
  template<size_t I, class... Types>
    constexpr const tuple_element_t<I, tuple<Types...>>&
      get(const tuple<Types...>&) noexcept;
  template<size_t I, class... Types>
    constexpr const tuple_element_t<I, tuple<Types...>>&&
      get(const tuple<Types...>&&) noexcept;
  template<class T, class... Types>
    constexpr T& get(tuple<Types...>& t) noexcept;
  template<class T, class... Types>
    constexpr T&& get(tuple<Types...>&& t) noexcept;
  template<class T, class... Types>
    constexpr const T& get(const tuple<Types...>& t) noexcept;
  template<class T, class... Types>
    constexpr const T&& get(const tuple<Types...>&& t) noexcept;
 
  // relational operators
  template<class... TTypes, class... UTypes>
    constexpr bool operator==(const tuple<TTypes...>&, const tuple<UTypes...>&);
  template<class... TTypes, class... UTypes>
    constexpr common_comparison_category_t</*synth-three-way-result*/<TTypes, UTypes>...>
      operator<=>(const tuple<TTypes...>&, const tuple<UTypes...>&);
 
  // allocator-related traits
  template<class... Types, class Alloc>
    struct uses_allocator<tuple<Types...>, Alloc>;
 
  // specialized algorithms
  template<class... Types>
    constexpr void
      swap(tuple<Types...>& x, tuple<Types...>& y) noexcept(/* see description */);
 
  // tuple helper classes
  template<class T>
    inline constexpr size_t tuple_size_v = tuple_size<T>::value;
}
 
// deprecated
namespace std {
  template<class T> class tuple_size<volatile T>;
  template<class T> class tuple_size<const volatile T>;
 
  template<size_t I, class T> class tuple_element<I, volatile T>;
  template<size_t I, class T> class tuple_element<I, const volatile T>;
}

Class template std::tuple

namespace std {
  template<class... Types>
  class tuple {
  public:
    // tuple construction
    constexpr explicit(/* see description */) tuple();
    constexpr explicit(/* see description */)
      tuple(const Types&...);         // only if sizeof...(Types) >= 1
    template<class... UTypes>
      constexpr explicit(/* see description */)
        tuple(UTypes&&...);           // only if sizeof...(Types) >= 1
 
    tuple(const tuple&) = default;
    tuple(tuple&&) = default;
 
    template<class... UTypes>
      constexpr explicit(/* see description */) tuple(const tuple<UTypes...>&);
    template<class... UTypes>
      constexpr explicit(/* see description */) tuple(tuple<UTypes...>&&);
 
    template<class U1, class U2>
      constexpr explicit(/* see description */)
        tuple(const pair<U1, U2>&);   // only if sizeof...(Types) == 2
    template<class U1, class U2>
      constexpr explicit(/* see description */)
        tuple(pair<U1, U2>&&);        // only if sizeof...(Types) == 2
 
    // allocator-extended constructors
    template<class Alloc>
      constexpr explicit(/* see description */)
        tuple(allocator_arg_t, const Alloc& a);
    template<class Alloc>
      constexpr explicit(/* see description */)
        tuple(allocator_arg_t, const Alloc& a, const Types&...);
    template<class Alloc, class... UTypes>
      constexpr explicit(/* see description */)
        tuple(allocator_arg_t, const Alloc& a, UTypes&&...);
    template<class Alloc>
      constexpr tuple(allocator_arg_t, const Alloc& a, const tuple&);
    template<class Alloc>
      constexpr tuple(allocator_arg_t, const Alloc& a, tuple&&);
    template<class Alloc, class... UTypes>
      constexpr explicit(/* see description */)
        tuple(allocator_arg_t, const Alloc& a, const tuple<UTypes...>&);
    template<class Alloc, class... UTypes>
      constexpr explicit(/* see description */)
        tuple(allocator_arg_t, const Alloc& a, tuple<UTypes...>&&);
    template<class Alloc, class U1, class U2>
      constexpr explicit(/* see description */)
        tuple(allocator_arg_t, const Alloc& a, const pair<U1, U2>&);
    template<class Alloc, class U1, class U2>
      constexpr explicit(/* see description */)
        tuple(allocator_arg_t, const Alloc& a, pair<U1, U2>&&);
 
    // tuple assignment
    constexpr tuple& operator=(const tuple&);
    constexpr tuple& operator=(tuple&&) noexcept(/* see description */);
 
    template<class... UTypes>
      constexpr tuple& operator=(const tuple<UTypes...>&);
    template<class... UTypes>
      constexpr tuple& operator=(tuple<UTypes...>&&);
 
    template<class U1, class U2>
      constexpr tuple& operator=(const pair<U1, U2>&); // only if sizeof...(Types) == 2
    template<class U1, class U2>
      constexpr tuple& operator=(pair<U1, U2>&&);      // only if sizeof...(Types) == 2
 
    // tuple swap
    constexpr void swap(tuple&) noexcept(/* see description */);
  };
 
  template<class... UTypes>
    tuple(UTypes...) -> tuple<UTypes...>;
  template<class T1, class T2>
    tuple(pair<T1, T2>) -> tuple<T1, T2>;
  template<class Alloc, class... UTypes>
    tuple(allocator_arg_t, Alloc, UTypes...) -> tuple<UTypes...>;
  template<class Alloc, class T1, class T2>
    tuple(allocator_arg_t, Alloc, pair<T1, T2>) -> tuple<T1, T2>;
  template<class Alloc, class... UTypes>
    tuple(allocator_arg_t, Alloc, tuple<UTypes...>) -> tuple<UTypes...>;
}