Standard library header <utility>

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library(C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library(C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library(C++17)

Regular expressions library(C++11)

Atomic operations library(C++11)

Thread support library(C++11)

Technical Specifications

 

Standard Library headers

Language Support
<cstddef> <cstdlib> <version> <limits> <climits>	<cfloat> <cstdint> <new> <typeinfo>	<source_location> <exception> <initializer_list> <compare>	<coroutine> <csignal> <csetjmp> <cstdarg>
Concepts
<concepts>
Diagnostics
<stdexcept>	<cassert>	<cerrno>	<system_error>
General utilities
<utility> <memory> <memory_resource> <scoped_allocator>	<bitset> <tuple> <optional> <any>	<variant> <type_traits> <ratio> <chrono>	<typeindex> <functional> <ctime>
Strings
<string> <string_view> <cstring>	<charconv> <format>	<cctype> <cwctype>	<cwchar> <cuchar>
Localization
<locale>	<codecvt>	<clocale>
Containers
<span> <array> <vector>	<deque> <forward_list> <list>	<map> <set> <queue>	<unordered_map> <unordered_set> <stack>
Iterators
<iterator>
Ranges
<ranges>
Algorithms
<algorithm>	<execution>
Numerics
<complex> <random>	<valarray> <numeric>	<bit> <numbers>	<cfenv> <cmath>
Input/Output
<iosfwd> <ios> <iomanip> <streambuf>	<istream> <ostream> <iostream>	<sstream> <fstream> <syncstream>	<cstdio> <cinttypes> <strstream>
Regular expressions
<regex>
Filesystem support
<filesystem>
Thread support
<thread> <atomic> <mutex>	<shared_mutex> <condition_variable> <future>	<stop_token> <semaphore>	<latch> <barrier>
C compatibility
<ciso646> <cstdalign>	<cstdbool> <ccomplex>	<ctgmath>

 

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 (function template)
move (C++11)	obtains an rvalue reference (function template)
move_if_noexcept (C++11)	obtains an rvalue reference 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 its argument for use in unevaluated context (function template)
cmp_equalcmp_not_equalcmp_lesscmp_greatercmp_less_equalcmp_greater_equal (C++20)	compares two integer values without value change caused by conversion (function template)
in_range (C++20)	checks if an integer value is in the range of a given integer type (function template)
make_pair	creates a pair object of type, defined 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)
std::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)
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)
Helpers
piecewise_construct_t (C++11)	tag type used to select correct function overload for piecewise construction (class)
piecewise_construct (C++11)	an object of type piecewise_construct_t used to disambiguate functions for piecewise construction (constant)
in_place in_place_type in_place_index in_place_t in_place_type_t in_place_index_t (C++17)	in-place construction tag (class template)

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>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;   // 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{};}   // 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, class U2>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
Utility library