Re: srfi-1 take and drop seriously broken

[Panicz Maciej Godek]

2016-11-20 11:42 GMT+01:00 Jan Synáček <address@hidden>:

>> 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.

Because someone might think that if he took 7 elements, then he has 7 elements, so it is good that he knows earlier that this is not the case. I don't see a point in referring to Haskell documentation when discussing Scheme functions, though (if you try Racket, you'll note that although its take has a reversed order of arguments compared to srfi-1, it still doesn't allow to take or drop a positive number of elements from an empty list)

I agree though that the srfi-1 document isn't explicit enough about this point.