Converting a Try[T] to a F[T] where F[_] is an effect

Question
1

I have an F[_] : cats.Applicative. I want to convert Try[T] to F[T].

val a: Try[T] = ???

val b: F[T] = a match {
case scala.util.Success(result) => implicitely[Applicative[F]].pure(result)
case scala.util.Failure(throwable) => ??? // what should go here?
2

You need an ApplicativeError[F, Throwable] instead of just an Applicative

Then you can just:

val b = ApplicativeError[F, Throwable].fromTry(a)
2 Likes
3

Can also use .liftTo syntax.

@ Try(1).liftTo[IO] 
res9: IO[Int] = Pure(1)

@ Try(???).liftTo[IO] 
res10: IO[Nothing] = RaiseError(scala.NotImplementedError: an implementation is missing)

@ Try(1).liftTo[Either[Throwable,*]] 
res11: Either[Throwable, Int] = Right(1)

@ Try(???).liftTo[Either[Throwable,*]] 
res12: Either[Throwable, A] = Left(scala.NotImplementedError: an implementation is missing)
2 Likes