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telekosmos/eithert-for-exception.scala

Created March 15, 2022 10:15
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EitherT for comprehensions
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eithert-for-exception.scala
import cats._
import cats.implicits._
import cats.effect._
import cats.data.EitherT
val res: EitherT[IO, Throwable, Unit] = for {
one <- EitherT[IO, Throwable, Int](IO(1.asRight[Throwable]))
// e <- EitherT(IO((new RuntimeException).asLeft[Int]))
two <- EitherT(IO(2.asRight[Throwable]))
} yield println(one + two)
val prog = IO { println(s"** Before ** ${Instant.now().toString}") } >> res.value >> IO { println(s"** After ** ${Instant.now().toString}") }
// val prog: cats.effect.IO[Unit] = IO(...)
prog.unsafeRunSync
** Before ** 2032-02-15T10:12:41.495Z
** After ** 2032-02-15T10:12:41.495Z
Raw
eithert-for-ok.scala
import cats._
import cats.implicits._
import cats.effect._
import cats.data.EitherT
val res: EitherT[IO, Throwable, Unit] = for {
one <- EitherT[IO, Throwable, Int](IO(1.asRight[Throwable]))
// e <- EitherT(IO((new RuntimeException).asLeft[Int]))
two <- EitherT(IO(2.asRight[Throwable]))
} yield println(one + two)
val prog = IO { println(s"** Before ** ${Instant.now().toString}") } >> res.value >> IO { println(s"** After ** ${Instant.now().toString}") }
// val prog: cats.effect.IO[Unit] = IO(...)
prog.unsafeRunSync
** Before ** 2032-02-15T10:12:41.495Z
3
** After ** 2032-02-15T10:12:41.495Z
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