Threads the expr through the forms. Inserts x as the
last item in the first form, making a list of it if it is not a
list already. If there are more forms, inserts the first form as the
last item in second form, etc.
;; get the sum of the first 10 even squares
user=> (->> (range)
(map #(* % %))
(filter even?)
(take 10)
(reduce +))
1140
;; this expands to:
user=> (reduce + (take 10 (filter even? (map #(* % %) (range)))))
1140
Source
clojure/core.clj:1540
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(defmacro ->>
"Threads the expr through the forms. Inserts x as the
last item in the first form, making a list of it if it is not a
list already. If there are more forms, inserts the first form as the
last item in second form, etc."
{:added "1.1"}
([x form] (if (seq? form)
(with-meta `(~(first form) ~@(next form) ~x) (meta form))
(list form x)))
([x form & more] `(->> (->> ~x ~form) ~@more)))
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