I'm trying to understand the difference between next and rest, so I've
taken clojure's implementation of some of the collection functions to view
how those functions use them. The source code of reduce is (I've marked in
red the calls than I do not understand).
(def
reduce
(fn r
([f coll]
(let [s (seq coll)]
(if s
(r f (first s) (next s))
(f))))
([f val coll]
(let [s (seq coll)]
(if s
(if (chunked-seq? s)
(recur f
(.reduce (chunk-first s) f val)
(chunk-next s))
(recur f (f val (first s)) (next s)))
val)))))
In the recur calls, the implementation uses next but the first think we do
with the collection is seq. I've always been told that (next s) == (seq
(rest s)) so, do we execute seq twice? Could the same recur call be done
using rest? What is more idiomatic?
Thanks,
Juan Manuel
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