How to reduce Seq[Either[A,B]] to Either[A,Seq[B]]?
Edit: I missed that the title of your question asked for Either[Seq[A],Seq[B]], but I did read “I’d like to obtain the first error message or a concatenation of all error messages”, and this would give you the former: def sequence[A, B](s: Seq[Either[A, B]]): Either[A, Seq[B]] = s.foldRight(Right(Nil): Either[A, List[B]]) { (e, acc) => for (xs … Read more