C++ Bitset::all() Function

The C++ function std::bitset::all() checks whether all the bits of the current bitset object are set (bits with value 1) or not.

The all() function takes no arguments and returns a boolean value 'true' if all the bits are 1; otherwise false. It has multiple applications, such as input validation and error detection, which involves checking if all bits are set to indicate an error in transmission.

The bitset class is a container that represents a fixed-size sequence of bits. Each bit in the bitset can have a value of either 0 or 1. The bitset class provides a number of member functions to manipulate individual bits of the bitset.

Syntax

Following is the syntax for std::bitset::all() −

bool all() const;

Parameters

This function does not accept any parameter.

Return value

Returns boolean value true or false.

Example 1

The following example shows the usage of std::bitset::all() using two bitsets.

Here, we are creating two bitsets "b" and "mask" with "4" bits each, setting "b" to the binary value "0000", and "mask" to the binary value "1111". Then, we are checking if the bits of "b" are set using the all() function. We are then performing a bitwise OR operation between "b" and "mask", and checking again if all the bits of "b" are set using the all() function.

#include <iostream>
#include <bitset>
using namespace std;

int main() {
   bitset<4> b("0000");
   bitset<4> mask("1111");
   if (b.all())
      cout << "All the bits of b are set" << endl;
   else
      cout << "All the bits of b are not set" << endl;
   b |= mask;
   if (b.all())
      cout << "All the bits of b are set" << endl;
   else
      cout << "All the bits of b are not set" << endl;
   return 0;
}

Output

Let us compile and run the above program, this will produce the following result −

All the bits of b are not set
All the bits of b are set

Example 2

Here, we are using the all() function to set all the bits of a bitset object.

In the following example, we are creating a bitset "b" of size "8". We are then setting all bits of "b" using the all() function.

#include <iostream>
#include <bitset>
using namespace std;

int main() {
   bitset<8> b;
   b.set().all();
   cout << "Binary value of b is " << b << endl;
   if (b.all())
      cout << "All the bits of b are set." << endl;
   else
      cout << "All the bits of are not set." << endl;
   return 0;
}

Output

If we run the above code it will generate the following output −

Binary value of b is 11111111
All the bits of b are set.

Example 3

In here, we are using the all() on a default bitset object.

In the following example, we are creating a default bitset (value of all the bits is 0) "b" of size "4". We are then checking if all the bits of "b" are set using the all() function.

#include <iostream>
#include <bitset>
using namespace std;

int main() {
   bitset<4> b;
   // default bitset will have default value of 0
   cout << "Binary value of b is " << b << endl;
   if (b.all())
      cout << "All the bits of b are set." << endl;
   else
      cout << "All the bits of b are not set." << endl;
   return 0;
}

Output

Following is the output of the above code −

Binary value of b is 0000
All the bits of b are not set.

Example 4

Here, we are creating a bitset "b" of size "4" with the binary value "1111". We are then performing a bitwise NOT operation on "b" and using the all() function to check if bits of "b" are set.

#include <iostream>
#include <bitset>
using namespace std;

int main() {
   bitset<4> b("1111");
   b = ~b;
   cout << "Binary value of b is " << b << endl;
   if (b.all())
      cout << "All the bits of b are set." << endl;
   else
      cout << "All the bits of b are not set." << endl;
   return 0;
}

Output

Output of the above code is as follows

Binary value of b is 0000
All the bits of b are not set.