Lists, rationals, polynomials and intervals - Implementation (types and basic operations) : Rat.div

let div_rat = function 

  Rat r1, Rat r2 -> if Num.eq_num r2 (Num.num_of_int 0)

                      then failwith ("div_rat : division by zero")

                      else Rat (Num.div_num r1 r2)