What do you assume when you see fromListN in a library?

[John Ky]

I should add that one of my actual use cases is to take a list of unknown
length and chunk it into a list of fixed sized vectors.

I use fromListN which allows me to fill a vector up until N and then I move
onto the next one etc until the list is exhausted.

Requiring an exact N is a pessimisation for me because it would force me to
create intermediate lists of the desired size before calling fromListN.

I do not mind if a function with the current behaviour exists but with a
different name like fromListUntilN or something similar.

On Fri, 28 Feb 2020 at 16:58, John Ky <newhoggy at gmail.com> wrote:

> I expect it to pre-allocate space for N elements and populate the vector
> until there are no more elements or the vector is full and return a vector
> that has a size the minimum of the length of the input list and N.
>
> To me size hint is definitely not what I want because it hides
> performance/allocation bugs.
>
> If it is possible to modify the function type then I would have it return
> a tuple of a vector with maximum size N as well as the remainder of the
> list.
>
> On Fri, 28 Feb 2020, 2:41 pm Zemyla, <zemyla at gmail.com> wrote:
>
>> I'm kind of the opposite. I think the number given to fromListN should be
>> a "size hint", not a redundant coding of the size of the list given.
>>
>> On Thu, Feb 27, 2020, 21:31 chessai . <chessai1996 at gmail.com> wrote:
>>
>>> I expect a list with precisely length N, and reject anything else. IIRC
>>> both primitive and vector do this
>>>
>>> On Thu, Feb 27, 2020, 6:54 PM Carter Schonwald <
>>> carter.schonwald at gmail.com> wrote:
>>>
>>>> Hey everyone:
>>>> When you see fromListN as a function in a library, do you assume /
>>>> presume it’s expecting an exactly N element list ? Or do you
>>>> expect/tolerate other behavior ?
>>>>
>>>> Should it reject shorter lists?
>>>>
>>>> Should it truncate or reject longer lists?
>>>>
>>>> A corner case of this came up in some bug discussion I was having
>>>> regarding vector,  and I shall claim and or presume that most folks assume
>>>> exact size with prompt rejection of too long or too short.
>>>>
>>>> Thoughts please ?
>>>>
>>>> -Carter
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