I think you've reinvented hashmaps:
{12 "a" 23 "aa" 25 "aaa" 234 "aaaa"}
On May 25, 6:51 pm, Andreas Kostler <andreas.koestler.le...@gmail.com>
wrote:
> Hi all,
> has anyone spent some thought on how to efficiently represent sparse vectors
> in Clojure?
> A naive scheme I came up with is using a vector of [idx val] pairs, e.g.:
> (def sparse-vec [[12 "a"][23 "aa"][25 "aaa"][234 "aaaa"]])
>
> Accessing a value at an idx can be done so:
> (get-nth sparse-vec 25)
> => "aaa"
>
> with:
>
> (defn get-nth [sparse-vec n]
> (let [indices (map (fn [[i _]] i) sparse-vec)
> idx (java.util.Collections/binarySearch indices n)
> [_ v] (nth sparse-vec idx)]
> v))
>
> For this to work the indices have to be in order. Can anyone think of more
> efficient (algorithmically and implementation wise)
> ways of doing this?
>
> Kind Regards
> Andreas
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