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

Carter Charbonneau zcarterc at gmail.com
Sat Jun 14 20:50:40 UTC 2014


On 06/14/2014 02:31 PM, Johan Tibell wrote:
> On Sat, Jun 14, 2014 at 10:15 PM, Carter Charbonneau <zcarterc at gmail.com
> <mailto: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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In real use of Category with only the (->) instance in scope, I don't 
run into complex error messages often, if ever. Do you have an example 
where complex error messages come into play?



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