C++ Bitset::operator<< Function

The C++ std::bitset::operator<< performs bitwise left SHIFT operation on the current bitset object. It stores the result in another (new) bitset object.

The bitwise left SHIFT operator shifts the bits of the operand to the left by the specified number of positions. The leftmost bits of the bitset object are discarded and a 0 bit is appended to the right end of the resultant binary value. The number of times we need to append a 0 bit depends on the number of positions that the bits are shifted.

A bitwise operator operates on individual bits of a binary number, rather than the whole number. It can be used to perform different operations, such as setting and clearing specific bits, checking if a bit is set or not, and manipulating data packed into bit fields.

Syntax

Following is the syntax for std::bitset::operator<< −

bitset operator<<(size_t pos) const;

Parameters

pos − Number of bits to be shifted.

Return value

Returns new bitset object which contains shifted bits.

Example 1

The following example shows the usage of std::bitset::operator<< on a single bitset operand.

Here, we are creating a bitset "b" of size "4" with the binary value "0001". Then we are shifting the bits of "b" one position to the left using the bitwise left shift operator and storing the result in a new variable "result".

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

int main(void) {
   bitset<4> b("0001");
   auto result = b << 1;
   cout << result << endl;
   return 0;
}

Output

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

0010

Example 2

Here, we are doubling an integer value using the operator<<.

In the following example, we are creating an integer variable "x" with an initial value of "10". Then, we are using the bitwise left shift operator to shift its bits to the left by one position, effectively doubling its value. We are then storing the result in a new variable "res".

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

int main(void) {
   int x = 10;
   int res = x << 1;
   cout << res << endl;
   return 0;
}

Output

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

20

Example 3

Now, we are setting a bit in a binary representation using the operator<<.

In the example given below, we are creating a 32-bit unsigned integer (non-negative values) variable called "mask" and assigning it with the hexadecimal value "0x01" (binary 0001). Then, we are using the bitwise left shift operator to move the binary digits of the original value to the left by "3" positions. We are then storing the result in a new variable "value".

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

int main(void) {
   uint32_t mask = 0x01;
   auto value = mask << 3;
   cout << value << endl;
   return 0;
}

Output

Following is an output of the above code −

8

Example 4

In here, we are shifting multiple values in an array to the left.

In the example below, we are creating an integer array "arr" with values "{16, 32, 64, 128}" (each value is formed by raising 2ⁿ). We are then creating an empty array "res" of size "4" to store the result in it. Then, we are shifting each element of the "arr" to the left by "4" bits using the bitwise left shift operator.

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

int main(void) {
   int arr[] = {16, 32, 64, 128};
   int res[4];
   for (int i = 0; i < 4; i++) {
      // left shift by 4 bits
      res[i] = arr[i] << 4;   
      cout << res[i] << " ";  
   } 
   return 0;
}

Output

We can see that each value in the array is multiplied by 2 raised to the power of 4 (i.e. 16), effectively increasing the value by a factor of 16 in the following output −

256 512 1024 2048