[Haskell-cafe] Call for comments: neither package
ivan.miljenovic at gmail.com
Tue Jun 29 01:24:45 EDT 2010
On 29 June 2010 15:20, Michael Snoyman <michael at snoyman.com> wrote:
> As far as I know, the only issue with depending on both is the conflicting
> orphan Monad instance for Either. Can anyone either confirm or deny this?
Since you're being naughty and using package-qualified imports, it
should be OK (in terms of working).
> On Tue, Jun 29, 2010 at 5:11 AM, Antoine Latter <aslatter at gmail.com> wrote:
>> It looks like good work, but I would be hesitent about depending on a
>> package which pulled in both mtl and tranformers.
>> Maybe that's just superstition - I haven't tried it.
>> On Jun 28, 2010 5:51 PM, "Michael Snoyman" <michael at snoyman.com> wrote:
>> Hi all,
>> I'll admit, the original idea for this package was something to place in
>> ACME ;). However, it's goal is to solve a real problem: the lack of good
>> instances on the Either type. As a brief summary, Either has no Applicative
>> or Monad instances in the base library, has 2 reasonable definitions for
>> Applicative, and there are conflicting orphan instances in the mtl and
>> transformers packages. Also, the ErrorT transformer in those two packages
>> introduces a superclass constraint many people would like to avoid.
>> neither supplies three datatypes: AEither, MEither and MEitherT. AEither
>> provides the Monoid version of the Applicative instance, MEither is the
>> monadic version, and MEitherT is a monad transformer. The package provides
>> instances for both the transformers and mtl libraries for MonadTrans,
>> MonadIO and MonadCatchIO.
>> The code is up on github, let me know what you think.
>>  http://github.com/snoyberg/neither
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Ivan Lazar Miljenovic
Ivan.Miljenovic at gmail.com
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