modular arithmetics

If you're working with bignum'bers, you'll probalby need to compare those two - are they equal, bigger, smaller etc.

My fix is connected with fact that is not always necessary to perform a modulo operation. For example: we have number a = 3, b = 4, modulus = 10. So, the operation would look something like that: (a + b) mod modulus = (3 + 4) mod 10 = 7 mod 10.