gistfile1.clj

(defn tricky-logic [x]
  (cond (or (cheap-test1)
            (expensive-test))
        (...body1...)
        (and (cheap-test2)
             (expensive-test))
        (...body2...)
        :else (expensive-test)))

;; rewrite to avoid repeating tests *or* code:

(defn tricky-logic [x]
  (let [expensive-results (delay (expensive-test))]
    (cond (or (cheap-test1)
              (force expensive-results))
          (...body1...)
          (and (cheap-test2)
               (force expensive-results))
          (...body2...)
          :else (force expensive-results))))