gistfile1.clj

(defmacro lazy-cons
  "Expands to code which produces a seq object whose first is
  first-expr and whose rest is rest-expr, neither of which is
  evaluated until first/rest is called. Each expr will be evaluated at most
  once per step in the sequence, e.g. calling first/rest repeatedly on the
  same node of the seq evaluates first/rest-expr once - the values they yield are
  cached."
 [first-expr & rest-expr]
 (list 'new 'clojure.lang.LazyCons (list `fn (list [] first-expr) (list* [(gensym)] rest-expr))))