Standard library header <utility>

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Standard Library header files

Language Support
<cstddef> <limits> <climits> <cfloat> <cstdint> <new> <typeinfo> <exception> <ciso646>	<initializer_list> <csignal> <csetjmp> <cstdalign> <cstdarg> <cstdbool> <cstdlib> <ctime>
Diagnostics
<stdexcept> <cassert>	<cerrno> <system_error>
General utilities
<utility> <tuple> <bitset> <memory> <cstdlib> <cstring> <functional>	<type_traits> <ratio> <chrono> <ctime> <scoped_allocator> <typeindex>
Strings
<string> <cctype> <cwctype> <cstring>	<cwchar> <cstdlib> <cuchar>
Localization
<locale> <codecvt> <clocale>

Containers
<array> <deque> <forward_list> <list> <vector>	<map> <set> <unordered_map> <unordered_set> <queue> <stack>
Iterators
<iterator>
Algorithms
<algorithm>	<cstdlib>
Numerics
<cfenv> <complex> <random> <valarray>	<numeric> <cmath> <ctgmath> <cstdlib>
Input/Output
<iosfwd> <iostream> <ios> <streambuf> <istream> <ostream>	<iomanip> <sstream> <fstream> <cstdio> <cinttypes>
Regular expressions
<regex>
Thread support
<thread> <mutex> <atomic>	<shared_mutex> <condition_variable> <future>

 

This header is part of the general utility library.

Includes
<initializer_list>(C++11)
Namespaces
rel_ops	Provide automatic comparison operators
Defined in namespace std::rel_ops
operator!=operator>operator<=operator>=	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)
declval (C++11)	obtains a reference to its argument for use in unevaluated context (function template)
make_pair	creates a pair object of type, defined by the argument types (function template)
operator==operator!=operator<operator<=operator>operator>=	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)
piecewise_construct_t (C++11)	tag type used to select correct function overload for piecewise construction (class)
integer_sequence (C++14)	implements compile-time sequence of integers (class template)
Forward declarations
tuple (C++11)	implements fixed size container, which holds elements of possibly different types (class template)
Objects
piecewise_construct (C++11)	an object of type piecewise_construct_t used to disambiguate functions for piecewise construction (constant)

Synopsis

#include <initializer_list>
 
namespace std {
    // operators:
    namespace 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&);
    }
 
    // swap:
    template<class T> void swap(T& a, T& b) noexcept(noexcept(a.swap(b));
    template <class T, size_t N> 
        void swap(T (&a)[N], T (&b)[N]) noexcept(noexcept(swap(*a, *b)));
 
    // exchange:
    template<class T, class U=T> T exchange(T& obj, U&& new_value);
 
    // forward/move:
    template <class T> T&& forward(typename remove_reference<T>::type& t) noexcept;
    template <class T> T&& forward(typename remove_reference<T>::type&& t) noexcept;
    template <class T> typename remove_reference<T>::type&& move(T&&) noexcept;
    template <class T> typename conditional<
        !is_nothrow_move_constructible<T>::value && is_copy_constructible<T>::value,
        const T&, T&&>::type move_if_noexcept(T& x) noexcept;
 
    // declval, as unevaluated operand:
    template <class T>
        typename add_rvalue_reference<T>::type declval() noexcept; 
 
    // pairs:
    template <class T1, class T2> struct pair;
 
    // pair specialized algorithms:
    template <class T1, class T2>
        bool operator==(const pair<T1,T2>&, const
    template <class T1, class T2>
        bool operator< (const pair<T1,T2>&, const pair<T1,T2>&);
    template <class T1, class T2>
        bool operator!=(const pair<T1,T2>&, const pair<T1,T2>&);
    template <class T1, class T2>
        bool operator> (const pair<T1,T2>&, const pair<T1,T2>&);
    template <class T1, class T2>
        bool operator>=(const pair<T1,T2>&, const pair<T1,T2>&);
    template <class T1, class T2>
        bool operator<=(const pair<T1,T2>&, const pair<T1,T2>&);
    template <class T1, class T2>
        void swap(pair<T1,T2>& x, pair<T1,T2>& y) noexcept(noexcept(x.swap(y)));
    template <class T1, class T2>
        pair<V1,V2> make_pair(T1&&, T2&&);
 
    //tuple-like access to pair:
    template <class T> class tuple_size;
    template <size_t I, class T> class tuple_element;
 
    template <class T1, class T2> struct tuple_size<std::pair<T1, T2> >;
    template <class T1, class T2> struct tuple_element<0, std::pair<T1, T2> >;
    template <class T1, class T2> struct tuple_element<1, std::pair<T1, T2> >;
 
    template<size_t I, class T1, class T2>
        typename tuple_element<I, std::pair<T1, T2> >::type& 
        get(std::pair<T1, T2>&) noexcept;
    template<size_t I, class T1, class T2>
        typename tuple_element<I, std::pair<T1, T2> >::type&& 
        get(std::pair<T1, T2>&&) noexcept;
    template<size_t I, class T1, class T2>
        const typename tuple_element<I, std::pair<T1, T2> >::type&
            get(const std::pair<T1, T2>&) noexcept;
 
    // pair piecewise construction
    struct piecewise_construct_t { };
    constexpr piecewise_construct_t piecewise_construct = piecewise_construct_t();
 
    template <class... Types> class tuple; // defined in <tuple>
}

Class std::pair

template <class T1, class T2>
struct pair {
    typedef T1 first_type;
    typedef T2 second_type;
 
    T1 first;
    T2 second;
    pair(const pair&) = default;
    pair(pair&&) = default;
 
    constexpr pair();
    pair(const T1& x, const T2& y);
    template<class U, class V> pair(U&& x, V&& y);
    template<class U, class V> pair(const pair<U, V>& p);
    template<class U, class V> pair(pair<U, V>&& p);
    template <class... Args1, class... Args2>
        pair(piecewise_construct_t,
             tuple<Args1...> first_args, tuple<Args2...> second_args);
 
    pair& operator=(const pair& p);
    template<class U, class V> pair& operator=(const pair<U, V>& p);
    pair& operator=(pair&& p) noexcept(see below);
    template<class U, class V> pair& operator=(pair<U, V>&& p);
 
    void swap(pair& p) noexcept( noexcept(swap(first, p.first)) &&
                                 noexcept(swap(second, p.second)) );
};

See also

<tuple>	Defines std::tuple
Utility library