I don't know if this is a *better* way, but I like it:
user=> (require '[clojure.algo.generic.functor :as f])
nil
user=> (def v [[:a 1] [:b 2] [:a 3] [:c 4] [:b 1]])
#'user/v
user=> (defn consolidate [m]
#_=> (f/fmap (partial apply +) (reduce (fn [acc [k v]] (update-in acc
[k] conj v)) {} m)))
#'user/consolidate
user=> (consolidate v)
{:c 4, :b 3, :a 4}
On Fri, Aug 16, 2013 at 9:57 PM, David Chelimsky <dchelim...@gmail.com>wrote:
> 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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--
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"Human kind has used its intelligence to vary the flavour of drinks, which
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