exact.clj

exact.clj

(defn exactify
  "take a multi-arity function and convert it to one that rationalizes all its arguments"
  [f]
  (fn
    ([] (f))
    ([x] (f (rationalize x)))
    ([x & items] (loop
                    [agg (rationalize x)
                     items items]
                    (if (empty? items)
                      agg
                      (recur (f agg (rationalize (first items))) (rest items)))))))

(defmacro exact
  "change an arithmetic operation to only operate on rational numbers"
  [form]
  `(let
    [+ (exactify +)
     - (exactify -)
     * (exactify *)
     / (exactify /)]
    ~form))

(macroexpand '(exact (* 2452.45 100)))