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ichramm/index-of.clj

Created August 28, 2020 14:47
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clojure index of element matching predicate
Raw
index-of.clj
(defn index-of
[pred coll]
(first (keep-indexed #(when (pred %2) %1) coll)))
; or
(defn indices
[pred coll]
(keep-indexed #(when (pred %2) %1) coll))
(def index-of (comp first indices))
(def last-index-of (comp last indices))
; or
(defn index-of
[pred coll]
(loop [coll coll idx 0]
(when (seq coll)
(if (pred (first coll))
idx
(recur (rest coll) (inc idx))))))
(defn last-index-of
[pred coll]
(loop [coll coll idx 0 e nil]
(if (seq coll)
(recur (rest coll)
(inc idx)
(if (pred (first coll)) idx e))
e)))
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