Hello samppi,
You could try this, the list does not really contain itself, but it
builds lists that are like itself recursively:
;builds recursion into lists, like Y the combinator
(defn build-recursive-list [fun list]
(fun (delay (build-recursive-list fun list)) list))
(def cyclic-list1
(build-recursive-list
(fn [self [a b c]] (lazy-cat [a b c] [(force self)])) [3 2 1]))
The second solution is simpler, but it looks a bit like a hack. cyclic-
list2 can contain itself becuase it is bound to a var before its
contents are evaluated.
(def cyclic-list2
(lazy-cat [3 2 1] [cyclic-list2]))
;It does realy contain ITSELF and not a list like itself
(let [[a b c self] cyclic-list2]
(= cyclic-list2 self))
(Well-intentioned advice: Don't try to print or otherwise completely
evaluate these lists or it will overflow your stack. Also don't
compare the first list to its self-similar elements, for the same
reason.)
hth, Robert Pfeiffer
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