I've got a vector of 2-element vectors e.g. [[:a 1] [:b 2]] where the first
val of any vec might appear in another vec e.g. [[:a 1] [:b 2] [:a 3]]. I
need a fn that will consolidate this into a hash-map with the vals
consolidated e.g.
(to-consolidated-map [[:a 1] [:b 2] [:a 3]])
; {:a 4 :b 2}
I've got two candidate implementations and I'm curious which you like
better and why, or if I'm missing a better way:
(defn to-consolidated-map [parts]
(reduce (fn [h [k v]]
(if (contains? h k)
(assoc h k (+ (k h) v))
(assoc h k v)))
{} parts))
(defn to-consolidated-map [parts]
(->> parts
(group-by first)
(map (fn [[k v]] [k (->> v (map last) (reduce +))]))))
TIA,
David
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