[Haskell-cafe] What is this applicative functor?

[Simon Jakobi]

Hi Joachim,

that's a very interesting type, thanks for sharing it!

Please note that in the rendering of the package description at
http://hackage.haskell.org/package/successors, the <*> is slightly
mangled.

Cheers,
Simon

2017-02-01 18:39 GMT+01:00 Joachim Breitner <mail at joachim-breitner.de>:
> Hi,
>
> Am Mittwoch, den 01.02.2017, 10:33 -0500 schrieb Joachim Breitner:
>> Hi,
>>
>> David wrote:
>> > How about this?
>> >
>> > hd (OneStep x xs) = x
>> >
>> > instance Monad OneStep where
>> >     OneStep x xs >>= f = OneStep y (map (hd . f) xs ++ ys)
>> >         where
>> >         OneStep y ys = f x
>> >
>> > Not sure if it’s good for anything, but it seems valid and consistent
>> > based on a preliminary investigation.
>>
>>
>> Yes, this looks reasonable. Did you happen to already work through the
>> monad laws?
>
> Just did, all looks fine:
> https://github.com/nomeata/haskell-successors/blob/c1fd614cb0fc3e3b5dbf0338f835a91ea78e0b63/src/Control/Applicative/Successors.hs#L82
>
> Uploaded to http://hackage.haskell.org/package/successors in case
> someone wants to play with it.
>
> Greetings,
> Joachim
> --
> Joachim “nomeata” Breitner
>   mail at joachim-breitner.de • https://www.joachim-breitner.de/
>   XMPP: nomeata at joachim-breitner.de • OpenPGP-Key: 0xF0FBF51F
>   Debian Developer: nomeata at debian.org
>
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