NAME¶

std::vector::reference - std::vector::reference

Synopsis¶

class reference;

The std::vector<bool, Alloc> specializations define std::vector<bool,
Alloc>::reference as a publicly-accessible nested class. std::vector<bool,
Alloc>::reference proxies the behavior of references to a single bit in
std::vector<bool, Alloc>.

The primary use of std::vector<bool, Alloc>::reference is to provide an lvalue that
can be returned from operator[].

Any reads or writes to a vector that happen via a std::vector<bool,
Alloc>::reference potentially read or write to the entire underlying vector.

Member functions¶

constructs the reference. Accessible only to std::vector<bool, Alloc>
constructor itself
(public member function)
destructor destroys the reference
(public member function)
operator= assigns a bool to the referenced bit
(public member function)
operator bool returns the referenced bit
(public member function)
flip flips the referenced bit
(public member function)

std::vector<bool, Alloc>::reference::~reference

~reference(); (until C++20)
constexpr ~reference(); (since C++20)

Destroys the reference.

std::vector<bool, Alloc>::reference::operator=

reference& operator=( bool x ); (until C++11)
reference& operator=( bool x ) noexcept; (since C++11)
(until C++20)
constexpr reference& operator=( bool x ) (since C++20)
noexcept;
reference& operator=( const reference& x ); (1) (until C++11)
reference& operator=( const reference& x ) (since C++11)
noexcept; (until C++20)
constexpr reference& operator=( const reference& (2) (since C++20)
x ) noexcept;
constexpr const reference& operator=( bool x ) (3) (since C++23)
const noexcept;

Assigns a value to the referenced bit.

Parameters¶

x - value to assign

Return value¶

*this

std::vector<bool, Alloc>::reference::operator bool

operator bool() const; (until C++11)
operator bool() const noexcept; (since C++11)
(until C++20)
constexpr operator bool() const noexcept; (since C++20)

Returns the value of the referenced bit.

Parameters¶

(none)

Return value¶

The referenced bit.

std::vector<bool, Alloc>::reference::flip

void flip(); (until C++11)
void flip() noexcept; (since C++11)
(until C++20)
constexpr void flip() noexcept; (since C++20)

Inverts the referenced bit.

Parameters¶

(none)

Return value¶

(none)

Helper classes¶

std::formatter<std::vector<bool, Alloc>::reference>

template < class T, class CharT >

requires /* is-vector-bool-reference */<T> (since C++23)

struct formatter<T, CharT>;

Specializes the std::formatter for std::vector<bool, Alloc>::reference. The
specialization uses std::formatter<bool, CharT> as its underlying formatter (denoted
as underlying_) where the referenced bit is converted to bool to be formatted.

The exposition-only constant /* is-vector-bool-reference */<T> is true if and only
if T denotes the type std::vector<bool, Alloc>::reference for some type Alloc and
std::vector<bool, Alloc> is not a program-defined specialization.

Member functions¶

template< class ParseContext > (1) (since C++23)
constexpr ParseContext::iterator parse( ParseContext& ctx );
template< class FormatContext >
FormatContext::iterator format( const T& r, FormatContext& ctx ) (2) (since C++23)
const;

1) Equivalent to return underlying_.parse(ctx);.
2) Equivalent to return underlying_.format(r, ctx);.

Example¶

This section is incomplete
Reason: no example

See also¶

operator[] access specified element
(public member function of std::vector<T,Allocator>)
swap swaps two std::vector<bool>::references
[static] (public static member function)

External links¶

"Effective Modern C++" by Scott Meyers (2015), Chapter 2, Item 6: "Use the
explicitly typed initializer idiom when auto deduces undesired types." (p.43-46) —
describes a possible misuse of the proxy class std::vector<bool>::reference).

Category:¶

* Todo no example