On Aug 9, 9:27 am, Chad Harrington <chad.harring...@gmail.com> wrote:
> Hi all,
> I am learning Clojure and would like to see if there is a better/more
> concise/faster/more idiomatic/etc. way to create the age-index below. My
> version seems awfully roundabout. The basic concept is a toy database table
> stored as a hashmap. Each row has a row-id and and a vector of data [name,
> age]. I then create an index on the age column. The index should yield a
> row-id for the given age value. My code below works as designed, but I'd
> like to see how the age-index could be improved.
>
> Thanks for your insights.
>
> Chad
> ------------ code begin ----------------
> (use '[clojure.contrib.seq-utils :only (flatten)])
>
> (def data {
> 0 ["Fred" 30],
> 1 ["Wilma" 26],
> 2 ["Bam-bam" 2],
> 3 ["Dino" 3]})
>
> (def age-index
> (apply sorted-map
> (flatten (map #(list
> (nth (val %) 1)
> (key %))
> data))))
The intent of the mapping can be made clearer with destructuring I
think. Also, flatten is not needed: a core function called "into" will
transform a sequence of key/value pairs into a map.
(def age-index
(into (sorted-map)
(map (fn [[k [name age]]] [age k]) data)))
> (defn name-by-age [age]
> (first (data (age-index age))))
>
> (println (name-by-age 26))
> ------------------ code end -------------------
>
> Chad Harrington
> chad.harring...@gmail.com
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