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std::vector<bool, Alloc>::reference - cppreference.com

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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
(public member function)
destroys the reference
(public member function)
assigns a value to the referenced bit
(public member function)
returns the referenced bit
(public member function) [edit]
flips the referenced bit
(public member function)

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

reference( const reference& ) = default;

 (since C++11)
(constexpr since C++20)

Constructs the reference from another reference. The copy constructor is implicitly declared.(until C++11)

Other constructors can only be accessed by std::vector<bool, Alloc>.

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

~reference();

 (constexpr since C++20)

Destroys the reference.

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

reference& operator=( bool x );

 (1) (noexcept since C++11)
(constexpr since C++20)

constexpr const reference& operator=( bool x ) const noexcept;

 (2) (since C++23)

reference& operator=( const reference& x );

 (3) (noexcept since C++11)
(constexpr since C++20)

Assigns a value to the referenced bit.

Parameters

Return value

*this

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

operator bool() const;

 (noexcept since C++11)
(constexpr since C++20)

Returns the value of the referenced bit.

Return value

The referenced bit.

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

void flip();

 (noexcept since C++11)
(constexpr since C++20)

Inverts the referenced bit.

Helper classes

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

template< class T, class CharT > requires /*is-vector-bool-reference*/<T> struct formatter<T, CharT>;

 (since C++23)

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 > constexpr ParseContext::iterator parse( ParseContext& ctx );

 (1) (since C++23)

template< class FormatContext > FormatContext::iterator format( const T& r, FormatContext& ctx ) const;

 (2) (since C++23)

1) Equivalent to return underlying_.parse(ctx);.

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

Example

See also

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

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).