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feat: +EitherT.liftRedeemK #4441

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feat: +EitherT.liftRedeemK #4441

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b189599
feat: +EitherT.liftRedeemK
GreyPlane May 19, 2023
8902a51
fix: fix scaladoc
GreyPlane May 19, 2023
1db5502
fix: fix scaladoc
GreyPlane May 20, 2023
9b99ea5
chore: rename function
GreyPlane May 23, 2023
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22 changes: 22 additions & 0 deletions core/src/main/scala/cats/data/EitherT.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -842,6 +842,28 @@ object EitherT extends EitherTInstances {
def apply[A](fa: F[A]): EitherT[F, E, A] = EitherT(F.attempt(fa))
}

/**
* Like [[liftAttemptK]] but gives your chance to map over original error.
*
* {{{
* scala> import cats._, data._, implicits._
* scala> val f: Unit => String = Function.const("panic!")
* scala> val a: Option[Int] = None
* scala> val b: EitherT[Option, String, Int] = EitherT.liftRedeemK[Option, Unit, String](f).apply(a)
* scala> b.value
* res0: Option[Either[String, Int]] = Some(Left(panic!))
*
* scala> val a2: Option[Int] = Some(42)
* scala> val b2: EitherT[Option, String, Int] = EitherT.liftRedeemK[Option, Unit, String](f).apply(a2)
* scala> b2.value
* res1: Option[Either[String, Int]] = Some(Right(42))
* }}}
*/
final def liftRedeemK[F[_], EA, EB](fe: EA => EB)(implicit F: ApplicativeError[F, EA]): F ~> EitherT[F, EB, *] =
new (F ~> EitherT[F, EB, *]) {
def apply[A](fa: F[A]): EitherT[F, EB, A] = EitherT(F.redeem(fa)(ea => Left(fe(ea)), Right.apply))
}

@deprecated("Use EitherT.liftF.", "1.0.0-RC1")
final def liftT[F[_], A, B](fb: F[B])(implicit F: Functor[F]): EitherT[F, A, B] = right(fb)

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