Op woensdag 30 april 2014 12:14:39 UTC+2 schreef James Reeves:
>
>
> On 30 April 2014 10:41, Roelof Wobben <[email protected] <javascript:>>wrote:
>
>>
>> Op woensdag 30 april 2014 09:58:26 UTC+2 schreef James Reeves:
>>
>>>
>>> Unlike vectors, seqs are simple structures and don't know their own
>>> length.
>>>
>>> You can count seqs, but this involves iterating through every element in
>>> turn. If all you want to do is find out whether there is more than one
>>> element, there's a much simpler and more efficient way.
>>>
>>>
>> Yep, if there is only 1 item is a list (rest coll) is nil.
>>
>
> Almost. Clojure distinguishes between nil and the empty list. The function
> you want is "next":
>
> (rest [1]) => ()
> (next [1]) => nil
>
> Why the distinction between next and rest? It has to do with laziness, and
> if you're interested I can go into more detail. Otherwise just remember
> that rest returns an empty list, and next returns nil.
>
>
> (defn last* [coll]
> (loop [coll coll]
> (if (nil? (next coll))
> (first coll)
> (recur (next coll))))
>
> Consider how you might add a counter to the loop. You'll want to increment
> the counter, then stop when it reaches the desired number.
>
So without checking it so out of my head I would do this
(defn last* [coll, number]
(loop [coll coll]
(if == counter number))
(first coll)
(recur (next coll) (+counter 1 ))
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