(defn short-name-seq
  "Lazy infinite seq of short names. like a,b,c..aa,bb,cc..zzzzz"
  []
  (let [letters (map str "abcdefghijklmnopqrstuvwxyz")]
    (mapcat (fn [length]
              (map (fn [letter] (apply str (repeat length letter))) letters))
            (range 1 Long/MAX_VALUE))))


; unit test

(deftest test-short-name-seq
  (let [short-names (vec (take 1000 (short-name-seq)))]
    (is (= (get short-names 0) "a"))
    (is (= (get short-names 1) "b"))
    (is (= (get short-names 25) "z"))
    (is (= (get short-names 26) "aa"))
    (is (= (get short-names 345) "hhhhhhhhhhhhhh"))
    (is (= (get short-names 733) "fffffffffffffffffffffffffffff"))))