XorT example

[pavlosgi]

I am trying to do

XorT.pure(eff)

where

eff: Eff[SomeEffect, Validated[E, A]]

and I get the following errors:

[error]  both value listInstance in trait ListInstances of type => cats.Traverse[List] with cats.MonadCombine[List] with cats.CoflatMap[List]
[error]  and value optionInstance in trait OptionInstances of type => cats.Traverse[Option] with cats.MonadCombine[Option] with cats.CoflatMap[Option] with cats.Alternative[Option]
[error]  match expected type cats.Applicative[F]
[error]     XorT.pure(s)

This is very weird since my Eff type has nothing to do with Option nor List. Weirdly if I do this:

XorT.pure(s)(optionInstance)

it compiles

[etorreborre]

Can you post a full gist with all your imports?

The other question is: what are you trying to achieve by mixing Eff and monad transformers?

[pavlosgi]

I'd like to use for comprehension with Eff and Xor

[pavlosgi]

I created this Gist where I am trying to do sequence to a List of effects and get the same error

[error]  both value function0Instance in trait Function0Instances of type => cats.Bimonad[Function0]
[error]  and value optionInstance in trait OptionInstances of type => cats.Traverse[Option] with cats.MonadCombine[Option] with cats.CoflatMap[Option] with cats.Alternative[Option]
[error]  match expected type cats.Applicative[G]
[error]   val efs = list.sequence

[pavlosgi]

I also created this Gist where I am trying to use XorT with Eff

[etorreborre]

This compiled for me with

import cats.std.list._
val efs = list.sequenceU

[pavlosgi]

Should have tried that, wasn't aware that cats also provides sequenceU like scalaz does. Yep that works for me as well and also list.traverseU(identity). Any ideas on XorT ? Thanks a lot btw

[etorreborre]

If you write XorT.pure(efs) just after val efs = list.sequenceU everything compiles ok.

[etorreborre]

I am closing this for now. Please feel free to discuss again on gitter.