gistfile1.cl

(def precedence {mod 0, * 1, / 1, + 2, - 2})

(defn find-split [exprs]  
  (loop [op-pos 1
         items exprs]
    (let [[x opa y opb] (take 4 items)]      
      (if (and opa opb (> (get precedence opa) (get precedence opb)))
        (recur 
          (+ op-pos 2)
          (drop 2 items))
        op-pos)) ))

(defn formula [& exprs]  
  (if (= (count exprs) 1)
    (if (number? (first exprs))
      (first exprs)
      (apply formula (first exprs)))
    (let [split (split-at (dec (find-split exprs)) exprs)
          [x op y] (take 3 (second split))] 
      (recur (into (conj 
                     (vec (first split)) 
                     (op (formula x) (formula y))) 
               (vec (drop 3 (second split))))))))