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std::bitset<N>::reference

class reference;

The std::bitset class includes std::bitset::reference as a publicly-accessible nested class. This class is used as a proxy object to allow users to interact with individual bits of a bitset, since standard C++ types (like references and pointers) are not built with enough precision to specify individual bits.

The primary use of std::bitset::reference is to provide an lvalue that can be returned from operator[].

Any reads or writes to a bitset that happen via a std::bitset::reference potentially read or write to the entire underlying bitset.

Member functions

(constructor)
 constructs the reference. Accessible only to std::bitset itself
(private 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)
operator~
 returns inverted referenced bit
(public member function)
flip
 flips the referenced bit
(public member function)

std::bitset<N>::reference::~reference 

~reference();
 (until C++23) 
constexpr ~reference();
 (since C++23)

Destroys the reference.

std::bitset<N>::reference::operator=

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

Assigns a value to the referenced bit.

Parameters

x - value to assign

Return value

*this.

std::bitset<N>::reference::operator bool 

operator bool() const;
 (until C++11) 
operator bool() const noexcept;
 (since C++11)
(until C++23) 
constexpr operator bool() const noexcept;
 (since C++23)

Returns the value of the referenced bit.

Parameters

(none).

Return value

The referenced bit.

std::bitset<N>::reference::operator~ 

bool operator~() const;
 (until C++11) 
bool operator~() const noexcept;
 (since C++11)
(until C++23) 
constexpr bool operator~() const noexcept;
 (since C++23)

Returns the inverse of the referenced bit.

Parameters

(none).

Return value

The inverse of the referenced bit.

std::bitset<N>::reference::flip 

reference& flip();
 (until C++11) 
reference& flip() noexcept;
 (since C++11)
(until C++23) 
constexpr reference& flip() noexcept;
 (since C++23)

Inverts the referenced bit.

Parameters

(none).

Return value

*this.

Example

#include <bitset>
#include <iostream>
 
int main()
{
    std::bitset<4> bs( 0b1110 );
 
    std::bitset<4>::reference ref = bs[2]; // auto ref = bs[2];
 
    auto info = [&](int n) {
        std::cout << n << ") bs: " << bs << "; ref bit: " << ref << '\n';
    };
 
    info(1);
    ref = false;
    info(2);
    ref = true;
    info(3);
    ref.flip();
    info(4);
    ref = bs[1]; // operator=( const reference& x )
    info(5);
 
    std::cout << "6) ~ref bit: " << ~ref << '\n';
}

Output:

1) bs: 1110; ref bit: 1
2) bs: 1010; ref bit: 0
3) bs: 1110; ref bit: 1
4) bs: 1010; ref bit: 0
5) bs: 1110; ref bit: 1
6) ~ref bit: 0

See also

accesses specific bit
(public member function)

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https://en.cppreference.com/w/cpp/utility/bitset/reference