NAME¶

std::bitset::reference - std::bitset::reference

Synopsis¶

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(); (constexpr since C++23)

Destroys the reference.

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

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

Inverts the referenced bit.

Parameters¶

(none)

Return value¶

*this

Example¶

// Run this code

#include <bitset>
#include <iostream>

int main()
{
std::bitset<4> bs{0b1110};

std::bitset<4>::reference ref = bs[2];

auto info = [&](int id)
{
std::cout << id << ") 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¶

operator[] accesses specific bit
(public member function)