The reduce in your mapped function is already implemented by get-in. Other
possible implementations using get-in:
(defn map-in [coll ks f & args]
(->> coll
(map #(get-in % ks))
(map #(apply f % args))))
Or:
(defn map-in [coll ks f & args]
(map #(apply f (get-in % ks) args) coll))
On Tuesday, March 24, 2015 at 9:16:58 PM UTC-5, Steve Ashton wrote:
>
> Is there anything for map which operates like update-in and assoc-in,
> where we can call a function with the value looked up in a nested structure?
>
> What I've come up with:
> (defn map-in
> "Returns a lazy sequence consisting of the results of
> calling map on coll, for each value in the coll,
> extracting the value using keys ks, finally applying f the
> that value and args: (apply f item args)"
> [coll [& ks] f & args]
> (map (fn [item]
> (let [value (reduce #(%2 %1) item ks)]
> (apply f value args)))
> coll))
>
> Which could then be used like:
> (def customers [{:name "Alice" :address {:city "Raleigh" :state "NC"}}
> {:name "Bob" :address {:city "Seattle" :state "WA"}}])
>
> (map-in customers [:address :state] #(-> % clojure.string/lower-case
> keyword))
> => (:nc :wa)
>
> Just wondering if I am re-inventing something here.
>
> Thanks,
> Steve
>
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