Thanks for the suggestions Sean and Ben. I learned new functions from both
of you!
Sean, your suggestion yields the following:
(to-consolidated-map [[:a 1] [:b 2] [:a 3]])
; {:a (1 3) :b (2)}
So it still needs to reduce the vals using +. That led me to this:
(defn to-consolidated-map [parts]
(apply merge-with + (map (fn [[k v]] {k v}) parts)))
Which led me to this:
(defn to-consolidated-map [parts]
(apply merge-with + (map (partial apply hash-map) parts)))
I like this one because it describes the solution the way I thought about
it - I just didn't know about merge-with. It also has the benefit of using
core fns rather than anonymous fns. WDYT?
On Sat, Aug 17, 2013 at 7:23 AM, Sean Corfield <[email protected]>wrote:
> How about this:
>
> (defn to-consolidated-map [parts]
> (apply merge-with concat
> (map (fn [[k v]] {k (list v)}) parts)))
>
> On Fri, Aug 16, 2013 at 9:57 PM, David Chelimsky <[email protected]>
> 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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