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std::bitset<N>::operator[]

	(1)
bool operator[]( std::size_t pos ) const;		(until C++11)
constexpr bool operator[]( std::size_t pos ) const;		(since C++11)
	(2)
reference operator[]( std::size_t pos );		(until C++23)
constexpr reference operator[]( std::size_t pos );		(since C++23)

Accesses the bit at position pos. The first version returns the value of the bit, the second version returns an object of type std::bitset::reference that allows modification of the value.

Unlike test(), does not throw exceptions: the behavior is undefined if pos is out of bounds.

Parameters

pos

position of the bit to return

Return value

1) the value of the requested bit

2) an object of type std::bitset::reference, which allows writing to the requested bit.

Exceptions

None.

Example

#include <iostream>
#include <bitset>
 
int main()
{
    std::bitset<8> b1{0b00101010}; // binary literal for 42
 
    for (std::size_t i = 0; i < b1.size(); ++i)
    {
        std::cout << "b1[" << i << "]: " << b1[i] << '\n';
    }
    b1[0] = true; // modifies the first bit through bitset::reference
 
    std::cout << "After setting bit 0, b1 holds " << b1 << '\n';
}

Output:

b1[0]: 0
b1[1]: 1
b1[2]: 0
b1[3]: 1
b1[4]: 0
b1[5]: 1
b1[6]: 0
b1[7]: 0
After setting bit 0, b1 holds 00101011

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.