std::bitset::operator[]

     bool operator[] (size_t pos) const;reference operator[] (size_t pos);

Access bit

The function returns the value (or a reference) to the bit at position pos.

With this operator, no range check is performed. Use bitset::test to access the value with bitset bounds checked.

Parameters

pos: Order position of the bit whose value is accessed.
Order positions are counted from the rightmost bit, which is order position 0.
size_t is an unsigned integral type.

Return value

The bit at position pos.

If the bitset object is const-qualified, the function returns a bool value. Otherwise, it returns a value of the special member type reference, which emulates a bool value with reference-semantics with respect to one bit in the bitset (see bitset::reference).

Example

// bitset::operator[]
#include <iostream>       // std::cout
#include <bitset>         // std::bitset

int main ()
{
  std::bitset<4> foo;

  foo[1]=1;             // 0010
  foo[2]=foo[1];        // 0110

  std::cout << "foo: " << foo << '\n';

  return 0;
}

Output:


foo: 0110

Data races

The bitset is accessed (neither the const nor the non-const versions modify the container).
The reference returned by the non-const version can be used to access or modify the bits in the bitset. Notice that modifying a single bit may have effects on an undetermined number of other bits in the bitset, thus rendering concurrent access/modification of different bits not thread-safe.

Exception safety

If pos is not a valid bit position, it causes undefined behavior.
Otherwise, if an exception is thrown by this member function, the bitset is left in a valid state (basic guarantee).

member classes

member functions