The "bitshift" is used to perform a bitwise shift on the input elements.
When the input is 0, the results always return the value of 2^n, no matter what the shift size n is.
e.g., bitshift(0, 4)=16 (10000)
bitshift(0, 8)=256 (100000000)
the behavior is same as the result for 1:
bitshift(1, 4)=16 (10000)