Re: srfi-1 take and drop seriously broken

[Jan Synáček]

On Sat, Nov 19, 2016 at 11:55 PM, Panicz Maciej Godek
<address@hidden> wrote:
>
>
> 2016-11-19 19:34 GMT+01:00 Jan Synáček <address@hidden>:
>>
>> Hi,
>>
>> scheme@(guile-user)> ,use (srfi srfi-1)
>> scheme@(guile-user)> (take (list 1 2 3) 4)
>> ERROR: In procedure list-head:
>> ERROR: In procedure list-head: Wrong type argument in position 1
>> (expecting pair): ()
>>
>> scheme@(guile-user) [1]> (drop (list 1 2 3) 4)
>> ERROR: In procedure list-tail:
>> ERROR: In procedure list-tail: Wrong type argument in position 1
>> (expecting pair): ()
>>
>> Please, tell me that this is just a mistake... This can't be true. I
>> still can't believe it. This is from 2.0.11. Please, tell me that the
>> implementation is fixed in 2.2.
>>
>> Yours truly puzzled,
>
>
> I don't know why you find it so puzzling. You can't take or drop something
> that "isn't there" (you can't take a car or cdr from an empty list as well,
> although e.g. in the language of "The Little Prover" (car '()) and (cdr '())
> both evaluate to '() to assure their totality). If you need, you can define
> your own variants that take/drop at most n elements of list.

Not only that you "can", it's also IMHO a fool-proof implementation
and I can't see any reason why it should behave differently.

https://hackage.haskell.org/package/base-4.8.2.0/docs/Data-List.html#v:take

Cheers,
-- 
Jan Synáček