gistfile1.clj

(defn exact-expr [expr]
  (cond (coll? expr) (map exact-expr expr)
        (number? expr) (rationalize expr)
        :else expr))

(defmacro exact [expr]
  (exact-expr expr))

(exact (* 2452.45 100))
;=> 245245N

(exact (+ (* 2.3 24) 12))
;=> 336/5