Proposal: add fromRight and fromLeft to Data.Either

David Feuer david.feuer at gmail.com
Sat May 21 13:10:38 UTC 2016


I'm sure he did, but I figured I should take the opportunity to point out
other ways to use those names.
On May 21, 2016 9:09 AM, "Christopher Allen" <cma at bitemyapp.com> wrote:

> I think Edward meant fromJust given the context.
>
> Sent from my iPhone
>
> On May 21, 2016, at 6:58 AM, David Feuer <david.feuer at gmail.com> wrote:
>
> No one wants to remove fromMaybe. In fact, it could serve as a template
> for total fromLeft and fromRight:
>
> fromLeft :: b -> (a -> b) -> Either a x -> b
> fromRight :: b -> (a -> b) -> Either x a -> b
> On May 21, 2016 8:55 AM, "Edward Kmett" <ekmett at gmail.com> wrote:
>
> I'm personally -1 on this.
>
> A large portion of the community is vehemently against adding new partial
> functions, and they have to share base with the rest of us. I'd say more
> people want to remove fromMaybe, head, tail, etc. than want to double down
> on the pattern at this time.
>
> -Edward
>
> On Fri, May 20, 2016 at 4:08 PM, Anton Felix Lorenzen <anfelor at posteo.de>
> wrote:
>
>> When working with Either,
>> I am often missing two simple functions:
>> fromRight :: Either a b -> b
>> fromLeft  :: Either a b -> a
>>
>> It has been implemented a couple of times:
>> http://hayoo.fh-wedel.de/?query=fromRight
>>
>> But I don't want to depend on yet another library
>> for such a basic function.
>>
>> Could it be added?
>>
>> Anton
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>>
>
>
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