Proposal: Num instance for (a -> b)

[Daniel Cartwright]

ANum seems to be just Data.Monoid.Ap.
Also, I can see not wanting to worsen the error messages, though it is
worth pointing out that we already have a Monoid instance with the same
semantics, and a similar potential for confusing error messages.

On Sun, Nov 11, 2018, 1:36 AM Dan Burton <danburton.email at gmail.com wrote:

> -1, per the very confusing errors that would ensue.
>
> If this behavior is desired, you can use a newtype wrapper. As it happens,
> this fits the pattern of ANum <http://hackage.haskell.org/package/ANum>.
> (Any Applicative can be made an instance of Num in this way.)
>
> -- Dan Burton
>
>
> On Sun, Nov 11, 2018 at 12:28 AM Tom Murphy <amindfv at gmail.com> wrote:
>
>> On 11/11/18, Henning Thielemann <lemming at henning-thielemann.de> wrote:
>> >
>> > On Sun, 11 Nov 2018, Henning Thielemann wrote:
>> >
>> >> On Sat, 10 Nov 2018, Daniel Cartwright wrote:
>> >>
>> >>> relevant reddit comment
>> >>> thread:
>> https://www.reddit.com/r/haskell/comments/9vtis5/the_universe_of_discourse_i_hate_the_environment/e9f1lea?utm_so
>> >>> urce=reddit-android
>> >>
>> >>
>> https://wiki.haskell.org/index.php?title=Num_instance_for_functions&oldid=36632
>> >>
>> >> In short: It would make 2(x+y) no longer a type error but equivalent
>> to 2.
>> >> We
>> >> would lose a lot of type safety for little syntactic gain.
>> >
>> > Btw. before adding more Wat instances please implement the GHC warning
>> > about such instances:
>> >     https://ghc.haskell.org/trac/ghc/ticket/11796
>>
>> This is my feeling as well.
>>
>> Tom
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