Mark partial functions as such

[David Feuer]

Yup! Just wanted to make sure it didn't end up being the latter.

On Thu, Aug 30, 2018, 10:19 PM Eric Mertens <emertens at gmail.com> wrote:

> I think this comes down to just documenting things like how strict
> functions are and how they behave on various classes of inputs. These are
> good things to document. It doesn’t just have to be about a boolean flag
> “partial” paste on a bunch of definitions.
>
> On Aug 30, 2018, at 7:16 PM, Daniel Díaz Casanueva <dhelta.diaz at gmail.com>
> wrote:
>
> Why not? I don't think mentioning that length doesn't work with infinite
> lists will do any harm.
>
> I think many people make a distinction between partiality due to endless
> evaluation and partiality due to a call to "error". But I still think
> documenting either of both things can be helpful.
>
> Best,
> Daniel
>
> Am Fr., 31. Aug. 2018 um 04:09 Uhr schrieb David Feuer <
> david.feuer at gmail.com>:
>
>> Yes, I think so. What about functions like length? length (repeat ()) is
>> bottom. repeat () is not bottom. Ergo, length is partial. But I don't think
>> we want to say that!
>>
>> On Thu, Aug 30, 2018, 10:05 PM Daniel Díaz Casanueva <
>> dhelta.diaz at gmail.com> wrote:
>>
>>> +1 from me too. The partiality of a function seems to me like something
>>> that should be documented.
>>>
>>> Best,
>>> Daniel
>>>
>>> Am Fr., 31. Aug. 2018 um 02:10 Uhr schrieb Richard Eisenberg <
>>> rae at cs.brynmawr.edu>:
>>>
>>>> Proposal: Mark partial functions in `base` as partial
>>>>
>>>> Motivation: I'm about to teach Haskell to a classful of beginners. In
>>>> my experience, they will soon reach for functions like `head` and `tail`,
>>>> because pattern-matching is foreign to them. I would love just to be able
>>>> to say "Don't use partial functions", but many students will not easily be
>>>> able to tell partial functions from total ones.
>>>>
>>>> I do expect this problem to work itself out rather quickly, and then
>>>> students will be able to identify partial functions, but loudly marking
>>>> partial functions as partial seems like a small service to everyone and a
>>>> bigger one to newbies. I don't see any downsides.
>>>>
>>>> Thoughts?
>>>>
>>>> Thanks,
>>>> Richard
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