[qznc]

In addition you must prevent overflows.

Microcents with signed long long (64bit) means a maximum value of 263 / 100 / (106) = 92233720368. In words "92 billion", which might not be enough.

[reeses]

In environments with exhaustive partitions and automatic 'promotion' (i.e., Common Lisp but probably not Ruby, etc.), your overflow would result in a correctly calculated bignum.

[GhotiFish]

yup! Which is scary to think about, because if you had a microcents requirement for accuracy, your ceiling would of being at 2^53/2*(micro) = 4,503,599,627

4 billion. eak.