gistfile1.txt

def foo():
    for x in range(5):
        yield x
        yield x*2

(letfn [(first [x]
          (lazy-seq
           (when (<= x 5)
            (cons x (second x)))))
        (second [x]
          (lazy-seq
           (cons (* 2 x)
                 (first (inc x)))))]
  (first 1))

;; (1 2 2 4 3 6 4 8 5 10)