Cumulative map

cmap.clj

(defn cmap
  "lazy cumulative map"
  ([f coll] (cmap f (f) coll))
  ([f val coll]
    (cons val
          (if (empty? coll)
            nil
            (lazy-seq (cmap f
                            (f val (first coll))
                            (rest coll))))))

(cmap + 0 '(1 1 1 1 1))
;; => (0 1 2 3 4 5)
(cmap + '(1 1 1 1 1))
;; => (0 1 2 3 4 5)
(cmap + 1 '(10 100 1000 10000 100000))
;; => (1 11 111 1111 11111 111111)
(cmap * '(10 10 2 0 99))
;; => (1 10 100 200 0 0)