Op dinsdag 6 mei 2014 12:40:24 UTC+2 schreef James Reeves:
>
> Well, == should be =, but more importantly you're mixing up number and
> counter.
>
> Step through your code one bit at a time:
>
> 1. You set number to 0
> 2. You set counter to (count coll) - 2
> 3. If number and counter are not equal...
> 4. Recur with the next part of the list, and set the counter to (+ number
> 1)
>
> See how you've got counter and number mixed up?
>
Yep,
So I change it to this :
(defn secondlast [coll]
(let [number 0 ]
(loop [coll coll counter (- (count coll)2)]
(if (= counter number)
(first coll)
(recur (next coll) (+ number 1))))))
But when I do (secondlast (list 1 2 3 4 5))
I still do not get a answer,
Roelof
> - James
>
>
> On 6 May 2014 11:24, Roelof Wobben <[email protected] <javascript:>>wrote:
>
>> I changed everything to this :
>>
>> (ns forclojure.core)
>> (defn secondlast [coll]
>> (let [number 0 ]
>> (loop [coll coll counter (- (count coll)2)]
>>
>> (if (== counter number)
>> (first coll)
>> (recur (next coll) (+ number 1))))))
>>
>>
>> But now I get a loop which never ends.
>>
>> Roelof
>>
>>
>> Op dinsdag 6 mei 2014 10:51:09 UTC+2 schreef Roelof Wobben:
>>
>>>
>>>
>>> Op dinsdag 6 mei 2014 10:43:40 UTC+2 schreef Benjamin R. Haskell:
>>>>
>>>> `loop` expects a vector of binding forms (with initial values), not
>>>> just a vector of names.
>>>>
>>>> (loop [coll counter] ; means there is one `loop` binding named
>>>> `coll`, with the initial value of `counter`
>>>>
>>>> To fix that problem directly:
>>>>
>>>> (loop [coll coll ; coll starts with an initial value of its
>>>> value outside the loop
>>>> counter counter] ; counter starts with an initial value of its
>>>> value outside the loop
>>>> ;; rest of code here ...
>>>>
>>>> Then you're left with an extra `let` (which was serving a similar
>>>> purpose to `loop` initialization?), and the whole `loop` is possibly
>>>> superfluous, because a function can be the target of a `recur`.
>>>>
>>>>
>>> oke, so I could do (loop [ coll coll counter 0] instead of the let ?
>>> And what do you mean with superfluous ??
>>>
>>> Roelof
>>>
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