> [snip]
>
> You are "accumulating" a result, which hints us at 'reduce.
> And 'for provides the nested enumeration:
>
> (defn floyd-warshall2 [{:keys [nodes distances]}]
> (reduce (fn [[distances prevs] [k x y]]
> (let [d (+ (distances [x k] Double/POSITIVE_INFINITY)
> (distances [k y] Double/POSITIVE_INFINITY))]
> (if (< d (distances [x y] Double/POSITIVE_INFINITY))
> [(assoc distances [x y] d) (assoc prevs [x y] k)]
> [distances prevs])))
> [distances {}] (for [k nodes x nodes y nodes] [k x y])))
>
> You should refrain from using indices or counters: most of the time, you can
> directly test a sequence. Why to maintain a counter to know whe you reach
> the end of a coll when (seq s) gives us this information and (next s)
> "decrements" the counter.
> (seehttp://clj-me.blogspot.com/2009/05/counting-without-numbers.html)
>
> Christophe
Hey, thanks.
Now that's elegant and short.
I would never thought of doing reduce with different argument types
(somehow it always seemed to me reduce is only for binary arithmetical
operations like + and *).
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