And this is mine

(defn keycollect-too [key-fn coll]
  (let [not-key (complement key-fn)]
    (loop [[k & more] coll, res (transient {})]
      (let [[vv rr] (split-with not-key more)]
        (if-not k
          (persistent! res)
          (recur rr (assoc! res k (vec vv))))))))

(keycollect-too keyword? [:key1 1 2 3 :key2 4 :key3 5 6 7]) => {:key1 [1 2 
3], :key2 [4], :key3 [5 6 7]}

Thanks.

On Wednesday, February 20, 2013 6:50:42 AM UTC-5, Stefan Kamphausen wrote:
>
> Hi,
>
> given a vector of the form
>
>  
>
>  [:key1 1 2 3 :key2 4 :key3 5 6 7]
>
> I wand to create a map collecting the items behind each keyword as a vector 
> like this:
>
>  {:key1 [1 2 3] 
>   :key2 [4] 
>   :key3 [5 6 7]}
>
> I have already written two functions which achieve this, but neither of them 
> "feels good" and I am interested in more elegant and idiomatic solutions.
>
> (defn keycollect-partition [coll]
>   (->> coll
>        (partition-by keyword?)      ; bundle at key
>        (partition 2)                ; kw + its arg
>        (map (fn [[[sec] arg]] [sec (vec arg)])) ; destruct the mess
>        (into {})))                 ; make it a map
>
> (defn keycollect-reduce [coll]
>   (apply zipmap
>          (reduce 
>           (fn [ac x] 
>             (if (keyword? x) 
>               [(conj (first ac) x) (conj (second ac) [])]
>               (update-in ac [1 (dec (count (first ac)))] conj x))) [[] []]
>               coll)))
>
> Added complexity: My original vector does not yet contain keywords, but I 
> construct them in a map regexp-matching each item and creating a keyword from 
> the first group of the match.
>
> Any pointers or ideas appreciated.
>
> Regards,
> Stefan
>
>  
>
>

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