CODEWITHSUNDEEP
clojure
estolua
estolua

Reputation: 676

Lazy self-recursive data structures in Clojure

Is there a way to describe arbitrary lazy self-recursive data structures in Clojure? Let's say for example I wanted to do something like this:

(def inf-seq (fn rec [] (lazy-seq (cons 42 (rec)))))
(take 3 (inf-seq))

but with a map:

(def inf-map (fn rec [] (??? {:a (rec) :b 42})))
(get-in (inf-map) [:a :a :a :b])

Upvotes: 2

Views: 335

Answers (1)

Jens
Jens

Reputation: 150

Sequence laziness does not apply to deferred function evaluation in Clojure, which you would obviously need for constructing infinitely nested maps.

Try using Delays:

user=> (def inf-map (fn rec [] {:a (delay (rec)) :b 42}))
#'user/inf-map
user=> (inf-map)
{:a #<Delay@4e9f9a19: :pending>, :b 42}
user=> @(:a (inf-map))
{:a #<Delay@5afd479c: :pending>, :b 42}

Upvotes: 2

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