qc-3.clj

(defn qc [op & pairs]
  (assert (even? (count pairs)))
  (fn [coll]
    (doseq [[pred msg] (partition 2 pairs)]
      (when-not (pred coll)
        (throw (IllegalArgumentException. msg))))
    (apply op coll)))

(def f1 (qc +
            #(= 2 (count %)) "coll must have length 2."
            #(even? (first %)) "first elem must be even."
            #(odd? (second %)) "second elem must be odd."))

(def f2 (qc -))
(def f3 (qc /))