EitherOps

Combine with another Either value.

If this Either is a Left then it will be returned as-is. If this Either is a Right and that Either is a left, then that will be returned. If both Eithers are Rights, then the Semigroup[BB] instance will be used to combine both values and return them as a Right. Note: If both Eithers are Lefts then their values are not combined. Use Validated if you prefer to combine Left values.

Examples:

scala> import cats.implicits._
scala> val l1: Either[String, Int] = Either.left("error 1")
scala> val l2: Either[String, Int] = Either.left("error 2")
scala> val r3: Either[String, Int] = Either.right(3)
scala> val r4: Either[String, Int] = Either.right(4)

scala> l1 combine l2
res0: Either[String, Int] = Left(error 1)

scala> l1 combine r3
res1: Either[String, Int] = Left(error 1)

scala> r3 combine l1
res2: Either[String, Int] = Left(error 1)

scala> r3 combine r4
res3: Either[String, Int] = Right(7)

lift the Either into a F[_] with ApplicativeError[F, A] instance

scala> import cats.implicits._
scala> import cats.data.EitherT
scala> val e: Either[String, Int] = Right(3)
scala> e.liftTo[EitherT[Option, CharSequence, *]]
res0: cats.data.EitherT[Option, CharSequence, Int] = EitherT(Some(Right(3)))

Transform the Either into a cats.data.EitherT while lifting it into the specified Applicative.

scala> import cats.implicits._
scala> val e: Either[String, Int] = Right(3)
scala> e.toEitherT[Option]
res0: cats.data.EitherT[Option, String, Int] = EitherT(Some(Right(3)))

Returns a cats.data.ValidatedNel representation of this disjunction with the Left value as a single element on the Invalid side of the cats.data.NonEmptyList.