Proposal to solve the `EitherT` problem.

Gabriel Gonzalez gabriel439 at gmail.com
Tue Aug 13 20:31:18 CEST 2013


I'm still in favor of adding `EitherT` to `transformers` in addition to
`ErrorT`.  The only person who disagreed the last discussion was Ross, so
it's a matter of convincing him.


On Tue, Aug 13, 2013 at 1:36 AM, David Luposchainsky <
dluposchainsky at googlemail.com> wrote:

> Morning,
>
> Another discussion that didn't reach conclusion: "Proposal to solve the
> `EitherT` problem." Let's do some proposal cleanup :-)
>
> On 2013-06-16 23:52, Gabriel Gonzalez wrote:
>
> > Approach 2: Add `EitherT` to `transformers` alongside `ErrorT` and
> have them both implement `MonadError`.
>
> That's the one I would recommend.
>
> - Doesn't break anything, and gets rid of the "exception-vs-error"
> discussion.
>
> - Not all uses of Either are to distinguish between success and failure,
> sometimes it's just a convenient way of short-circuiting.
>
> - Fits in well with all the other transformers of type "MonadT".
>
> - MonadError instance makes possible use as throw-catch-y transformer
> clear.
>
>
>
> David
>
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