bit_operation.py

"""
Fundamental bit operation:
    get_bit(num, i): get an exact bit at specific index
    set_bit(num, i): set a bit at specific index
    clear_bit(num, i): clear a bit at specific index
    update_bit(num, i, bit): update a bit at specific index
"""

"""
This function shifts 1 over by i bits, creating a value being like 0001000. By
performing an AND with num, we clear all bits other than the bit at bit i.
Finally we compare that to 0
"""
def get_bit(num, i):
    return (num & (1 << i)) != 0

"""
This function shifts 1 over by i bits, creating a value being like 0001000. By
performing an OR with num, only value at bit i will change.
"""
def set_bit(num, i):
    return num | (1 << i)

"""
This method operates in almost the reverse of set_bit
"""
def clear_bit(num, i):
    mask = ~(1 << i)
    return num & mask

"""
To set the ith bit to value, we first clear the bit at position i by using a
mask. Then, we shift the intended value. Finally we OR these two numbers
"""
def update_bit(num, i, bit):
    mask = ~(1 << i)
    return (num & mask) | (bit << i)