Standard library header <utility>

 

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Language support <cfloat> <climits> <compare>(C++20) <contracts>(C++26) <coroutine>(C++20) <csetjmp> <csignal> <cstdarg> <cstddef> <cstdint>(C++11) <cstdlib> <exception> <initializer_list>(C++11)    <limits> <new> <source_location>(C++20) <stdfloat>(C++23) <typeinfo> <version>(C++20) Concepts <concepts>(C++20) Diagnostics <cassert> <cerrno> <debugging>(C++26) <stacktrace>(C++23) <stdexcept> <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 <any>(C++17) <bitset> <bit>(C++20) <charconv>(C++17) <expected>(C++23) <format>(C++20) <functional> <optional>(C++17) <stdbit.h>(C++26) <tuple>(C++11) <typeindex>(C++11) <utility> <variant>(C++17) Containers <array>(C++11) <deque> <flat_map>(C++23) <flat_set>(C++23) <forward_list>(C++11) <hive>(C++26) <inplace_vector>(C++26)    <list> <map> <mdspan>(C++23) <queue> <set> <span>(C++20) <stack> <unordered_map>(C++11) <unordered_set>(C++11) <vector> Iterators <iterator> Ranges <generator>(C++23) <ranges>(C++20)

Algorithms <algorithm> <numeric> Strings <cctype> <cstring> <cuchar>(C++11) <cwchar> <cwctype> <string_view>(C++17) <string> Text processing <clocale> <codecvt>(C++11/17/26*) <locale> <regex>(C++11) <text_encoding>(C++26)    Numerics <cfenv>(C++11) <cmath> <complex> <linalg>(C++26) <numbers>(C++20) <random>(C++11) <simd>(C++26) <stdckdint.h>(C++26) <valarray> Time <chrono>(C++11) <ctime> C compatibility <ccomplex>(C++11/17/20*) <ciso646>(until C++20) <cstdalign>(C++11/17/20*) <cstdbool>(C++11/17/20*) <ctgmath>(C++11/17/20*)

Input/output <cinttypes>(C++11) <cstdio> <filesystem>(C++17) <fstream> <iomanip> <iosfwd> <iostream> <ios> <istream> <ostream> <print>(C++23) <spanstream>(C++23) <sstream> <streambuf> <strstream>(C++98/26*) <syncstream>(C++20) Concurrency support <atomic>(C++11) <barrier>(C++20) <condition_variable>(C++11) <future>(C++11) <hazard_pointer>(C++26) <latch>(C++20) <mutex>(C++11) <rcu>(C++26) <semaphore>(C++20) <shared_mutex>(C++14) <stdatomic.h>(C++23) <stop_token>(C++20) <thread>(C++11) Execution support <execution>(C++17)

 

This header is part of the general utility library.

Includes
<compare> (C++20)	Three-way comparison operator support
<initializer_list> (C++11)	std::initializer_list class template
Namespaces
rel_ops	Provide automatic comparison operators
Defined in namespace std::rel_ops
operator!=operator>operator<=operator>= (deprecated in C++20)	automatically generates comparison operators based on user-defined operator== and operator< (function template)
Functions
swap	swaps the values of two objects (function template)
exchange (C++14)	replaces the argument with a new value and returns its previous value (function template)
forward (C++11)	forwards a function argument and use the type template argument to preserve its value category (function template)
forward_like (C++23)	forwards a function argument as if casting it to the value category and constness of the expression of specified type template argument (function template)
move (C++11)	converts the argument to an xvalue (function template)
move_if_noexcept (C++11)	converts the argument to an xvalue if the move constructor does not throw (function template)
as_const (C++17)	obtains a reference to const to its argument (function template)
declval (C++11)	obtains a reference to an object of the template type argument for use in an unevaluated context (function template)
to_underlying (C++23)	converts an enumeration to its underlying type (function template)
cmp_equalcmp_not_equalcmp_lesscmp_greatercmp_less_equalcmp_greater_equal (C++20)	compares two integer values, ensuring that signed negative numbers are less than unsigned numbers (function template)
in_range (C++20)	checks if an integer value is in the range of a given integer type (function template)
unreachable (C++23)	marks unreachable point of execution (function)
make_pair	creates a pair object of type, determined by the argument types (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 pair (function template)
std::swap(std::pair) (C++11)	specializes the std::swap algorithm (function template)
get(std::pair) (C++11)	accesses an element of a pair (function template)
Classes
pair	implements binary tuple, i.e. a pair of values (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::pair> (C++11)	obtains the size of a pair (class template specialization)
std::tuple_element<std::pair> (C++11)	obtains the type of the elements of pair (class template specialization)
integer_sequence (C++14)	implements compile-time sequence of integers (class template)
Forward declarations
Defined in header <tuple>
tuple (C++11)	implements fixed size container, which holds elements of possibly different types (class template)
Defined in header <variant>
monostate (C++17)	placeholder type for use as the first alternative in a variant of non-default-constructible types (class)
Constants
ignore (C++11)	placeholder to skip an element when unpacking a tuple using tie (constant)
Tags
piecewise_constructpiecewise_construct_t (C++11)	piecewise construction tag (tag)
in_placein_place_typein_place_indexin_place_tin_place_type_tin_place_index_t (C++17)	in-place construction tag (tag)
nontype nontype_t (C++26)	value construction tag (tag)

Synopsis

#include <compare>#include <initializer_list>   namespace std {// swaptemplate<class T>constexprvoid swap(T& a, T& b)noexcept(/* see description */);template<class T, size_t N>constexprvoid swap(T (&a)[N], T (&b)[N])noexcept(is_nothrow_swappable_v<T>);   // exchangetemplate<class T, class U = T>constexpr T exchange(T& obj, U&& new_val);   // forward/movetemplate<class T>constexpr T&& forward(remove_reference_t<T>& t)noexcept;template<class T>constexpr T&& forward(remove_reference_t<T>&& t)noexcept;template<class T, class U>constexpr/* see description */ forward_like(U&& x)noexcept;template<class T>constexpr remove_reference_t<T>&& move(T&&)noexcept;template<class T>constexpr conditional_t<!is_nothrow_move_constructible_v<T>&& is_copy_constructible_v<T>, const T&, T&&> move_if_noexcept(T& x)noexcept;   // as_consttemplate<class T>constexpr add_const_t<T>& as_const(T& t)noexcept;template<class T>void as_const(const T&&)= delete;   // declvaltemplate<class T> add_rvalue_reference_t<T> declval()noexcept;// as unevaluated operand   // integer comparison functionstemplate<class T, class U>constexprbool cmp_equal(T t, U u)noexcept;template<class T, class U>constexprbool cmp_not_equal(T t, U u)noexcept;   template<class T, class U>constexprbool cmp_less(T t, U u)noexcept;template<class T, class U>constexprbool cmp_greater(T t, U u)noexcept;template<class T, class U>constexprbool cmp_less_equal(T t, U u)noexcept;template<class T, class U>constexprbool cmp_greater_equal(T t, U u)noexcept;   template<class R, class T>constexprbool in_range(T t)noexcept;   // to_underlyingtemplate<class T>constexpr underlying_type_t<T> to_underlying(T value)noexcept;   // unreachable[[noreturn]]void unreachable();   // compile-time integer sequencestemplate<class T, T...>struct integer_sequence;template<size_t... I>using index_sequence = integer_sequence<size_t, I...>;   template<class T, T N>using make_integer_sequence = integer_sequence<T, /* see description */>;template<size_t N>using make_index_sequence = make_integer_sequence<size_t, N>;   template<class... T>using index_sequence_for = make_index_sequence<sizeof...(T)>;   // class template pairtemplate<class T1, class T2>struct pair;   // pair specialized algorithmstemplate<class T1, class T2>constexprbool operator==(const pair<T1, T2>&, const pair<T1, T2>&);template<class T1, class T2>constexpr common_comparison_category_t</*synth-three-way-result*/<T1>, /*synth-three-way-result*/<T2>> operator<=>(const pair<T1, T2>&, const pair<T1, T2>&);   template<class T1, class T2>constexprvoid swap(pair<T1, T2>& x, pair<T1, T2>& y)noexcept(noexcept(x.swap(y)));   template<class T1, class T2>constexpr/* see description */ make_pair(T1&&, T2&&);   // tuple-like access to pairtemplate<class T>struct tuple_size;template<size_t I, class T>struct tuple_element;   template<class T1, class T2>struct tuple_size<pair<T1, T2>>;template<size_t I, class T1, class T2>struct tuple_element<I, pair<T1, T2>>;   template<size_t I, class T1, class T2>constexpr tuple_element_t<I, pair<T1, T2>>& get(pair<T1, T2>&)noexcept;template<size_t I, class T1, class T2>constexpr tuple_element_t<I, pair<T1, T2>>&& get(pair<T1, T2>&&)noexcept;template<size_t I, class T1, class T2>constexprconst tuple_element_t<I, pair<T1, T2>>& get(const pair<T1, T2>&)noexcept;template<size_t I, class T1, class T2>constexprconst tuple_element_t<I, pair<T1, T2>>&& get(const pair<T1, T2>&&)noexcept;template<class T1, class T2>constexpr T1& get(pair<T1, T2>& p)noexcept;template<class T1, class T2>constexprconst T1& get(const pair<T1, T2>& p)noexcept;template<class T1, class T2>constexpr T1&& get(pair<T1, T2>&& p)noexcept;template<class T1, class T2>constexprconst T1&& get(const pair<T1, T2>&& p)noexcept;template<class T2, class T1>constexpr T2& get(pair<T1, T2>& p)noexcept;template<class T2, class T1>constexprconst T2& get(const pair<T1, T2>& p)noexcept;template<class T2, class T1>constexpr T2&& get(pair<T1, T2>&& p)noexcept;template<class T2, class T1>constexprconst T2&& get(const pair<T1, T2>&& p)noexcept;   // pair piecewise constructionstruct piecewise_construct_t {explicit piecewise_construct_t()=default;};inlineconstexpr piecewise_construct_t piecewise_construct{};template<class... Types>class tuple;// defined in <tuple>   // in-place constructionstruct in_place_t {explicit in_place_t()=default;};inlineconstexpr in_place_t in_place{};   template<class T>struct in_place_type_t {explicit in_place_type_t()=default;};template<class T>inlineconstexpr in_place_type_t<T> in_place_type{};   template<size_t I>struct in_place_index_t {explicit in_place_index_t()=default;};template<size_t I>inlineconstexpr in_place_index_t<I> in_place_index{};   // nontype argument tagtemplate<auto V>struct nontype_t {explicit nontype_t()=default;};template<auto V>inlineconstexpr nontype_t<V> nontype{};}   // deprecatednamespace std::rel_ops{template<class T>bool operator!=(const T&, const T&);template<class T>bool operator>(const T&, const T&);template<class T>bool operator<=(const T&, const T&);template<class T>bool operator>=(const T&, const T&);}

Class template std::integer_sequence

namespace std {template<class T, T... I>struct integer_sequence {using value_type = T;staticconstexpr size_t size()noexcept{return sizeof...(I);}};}

Class template std::pair

namespace std {template<class T1, class T2>struct pair {using first_type = T1;using second_type = T2;   T1 first; T2 second;   pair(const pair&)=default; pair(pair&&)=default;constexprexplicit(/* see description */) pair();constexprexplicit(/* see description */) pair(const T1& x, const T2& y);template<class U1 = T1, class U2 = T2>constexprexplicit(/* see description */) pair(U1&& x, U2&& y);template<class U1, class U2>constexprexplicit(/* see description */) pair(const pair<U1, U2>& p);template<class U1, class U2>constexprexplicit(/* see description */) pair(pair<U1, U2>&& p);template<class... Args1, class... Args2>constexpr pair(piecewise_construct_t, tuple<Args1...> first_args, tuple<Args2...> second_args);   constexpr pair& operator=(const pair& p);template<class U1, class U2>constexpr pair& operator=(const pair<U1, U2>& p);constexpr pair& operator=(pair&& p)noexcept(/* see description */);template<class U1, class U2>constexpr pair& operator=(pair<U1, U2>&& p);   constexprvoid swap(pair& p)noexcept(/* see description */);};   template<class T1, class T2> pair(T1, T2)-> pair<T1, T2>;}

See also

<tuple> (C++11)

std::tuple class template