Proposal: Use (.) and id from Control.Category in Prelude

Iavor Diatchki iavor.diatchki at gmail.com
Sun Jun 15 01:18:47 UTC 2014


-2.   Please don't.  The status quo works well enough, and is sufficient
for many many cases (in fact all I've ever encountered).  Folks who need
more already have a perfectly reasonable way to get it: simply use the
overloaded operators from `Control.Category`.

-Iavor


On Sat, Jun 14, 2014 at 2:10 PM, Sjoerd Visscher <sjoerd at w3future.com>
wrote:

> I strongly disagree, this would benefit all Haskell users, and will
> improve error messages!
>
> Packages like lens now jump through hoops to be able to do composition
> with the Prelude (.), making proper abstraction impossible, resulting in
> horrible error messages spewing the internals of the library to the
> unsuspecting user.
>
> Composition is very important for modular code, and should be made as
> accessible to all users as possible.
>
> Sjoerd
>
> On 14 Jun 2014, at 22:31, Johan Tibell <johan.tibell at gmail.com> wrote:
>
> On Sat, Jun 14, 2014 at 10:15 PM, Carter Charbonneau <zcarterc at gmail.com>
> wrote:
>
>> (.) and id are generalized in the Category class in Control.Category. In
>> the past, many libraries have instructed users to use (.) and id from
>> Control.Category for composition of their types. Importing these types into
>> Prelude shouldn't break existing code, and makes libraries that use
>> Category easier to use.
>>
>> Discussion period: 4 weeks
>>
>
> -1
>
> This would benefit very few Haskell users and make error messages terrible.
>
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