TheseT monad transformer (plus IO instances and tests) #1162
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Not sure what this failure is - it doesn't look obvious that it's actually anything to do with the PR (appears to be in MiMa and something to do with the JS backend) |
| @@ -256,6 +256,9 @@ object ScalazArbitrary { | |||
| implicit def eitherTArb[F[+_], A, B](implicit A: Arbitrary[F[A \/ B]]): Arbitrary[EitherT[F, A, B]] = | |||
| Functor[Arbitrary].map(A)(EitherT[F, A, B](_)) | |||
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| implicit def theseTArb[F[+_], A, B](implicit A: Arbitrary[F[A \&/ B]]): Arbitrary[TheseT[F, A, B]] = | |||
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implicit def theseTArb[F[_], A, B]
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I have made this change
Conflicts: core/src/main/scala/scalaz/TheseT.scala
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| def &&&[AA >: A, C](t: TheseT[F, AA, C])(implicit M: Semigroup[AA], F: Apply[F]): TheseT[F, AA, (B, C)] | ||
| = TheseT(F.apply2(run, t.run)(_ &&& _)) | ||
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| def ===[AA >: A, BB >: B](x: TheseT[F, AA, BB])(implicit EA: Equal[AA], EB: Equal[BB], F: Apply[F]): F[Boolean] |
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I think we should define Equal[TheseT[F, A, B] instance and then remove this method. WDYT?
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EitherT defines both === as an instance method on EitherT (along the lines of the above) and also a Equal instance (in EitherTInstances) [1]. This is presumably a mistake [2] and I took the view that the former was more useful because the most common value for F is presumably IO (or a stack with IO in it) and thus there will be no implicit Equal[EitherT[F, A, B]]
I do agree that the instance method === with a return type other than Boolean is a bit iffy; I was just trying to keep TheseT as close to EitherT as possible
[1] -
implicit def eitherTEqual[F[_], A, B](implicit F0: Equal[F[A \/ B]]): Equal[EitherT[F, A, B]]
= F0.contramap((_: EitherT[F, A, B]).run)
[2] - just because et1 === et2 is never using the typeclass but the instance method
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I did as you ask because I just can't take the silent treatment anymore
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sorry for the delay. 75935e138206a8fbf is LGTM
| type TheseTListInt[A] = TheseT[List, Int, A] | ||
| type TheseTOptionInt[A] = TheseT[Option, Int, A] | ||
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| implicit def TheseTListIntEqual[A: Equal]: Equal[TheseTListInt[A]] = new Equal[TheseTListInt[A]] { |
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I think this is unnecessary because now there is implicit def theseTEqual in ThereT.scala.
* Added TheseT and MonadIO/LiftIO/MonadCatchIO instances * Added tests for laws for TheseT * Added EitherT.toThese * requested removing variance annotation * requested removing the TheseTFunctions trait * Added TheseT and MonadIO/LiftIO/MonadCatchIO instances * Added tests for laws for TheseT * Added EitherT.toThese * requested removing variance annotation * requested removing the TheseTFunctions trait * use kind projector for M[_[_], _] * removed === in favour of Equal[TheseT[?[_], ?, ?] * Removed unnecessary implicit
TheseT is a monad transformer for
\&/(pronounced these).A \&/ Brepresents having either anA, or aB, or bothTheseT[M, A, B]is essentially an ops class for aM[A \&/ B]. TheseT is both a monad and it supports many of the operations one finds on\&/