Probably the biggest gift we can get by using immutability are the pure functions (covered in the next chapter). Basically, pure functions and immutability are not only companions, but are complimentary to each other.

We cannot implement pure functions without immutability and immutability isn't complete without pure functions.

So, as we've learned a lot about immutability and its advantages, let us now focus on the other side: the disadvantages of immutability and check if they truly are disadvantages.