Numbers.ZSourceIntegers implementation. *
convert to machine integer. returns None in case of overflow
Shifts left by (n:int >= 0) bits. This is the same as t * pow(2,n)
returns sqrt truncated with the remainder. It assumes that the argument is positive, otherwise, Invalid_argument is raised.
testbit z n returns true iff the nth bit of z is set to 1. n is supposed to be positive