| def retry[F[_]: Monad, E, A](f: => EitherT[F, E, A])(n: Int): EitherT[F, List[E], A] = | |
| Stream.fill(n)(f).traverseU(_.swap).map(_.toList).swap |
Say we have a morally correct json library.
It comes with types like: JValue, JObject and Path.
It also has error types extending JsonError like ParsingError, CastingError and FieldError. To make it even smarter, there's a sweet Semigroup[JsonError] to accumulate errors properly (left as an exercise).
Finally, there are a bunch of basic combinators:
def parse(in: String): ParsingError \/ JValue
| object jsonExample { | |
| import scala.language.higherKinds | |
| import scalaz._, Scalaz._ | |
| type Path = String | |
| type JValue | |
| type JObject | |
| implicit class RichDisjunction[A, B](disjunction: A \/ B) { |
| trait HasInverse[A] | |
| object HasInverse { | |
| def apply[A]: HasInverse[A] = new HasInverse[A] {} | |
| } | |
| implicit def dummyHasInverse[A]: HasInverse[A] = HasInverse[A] | |
| trait Inverse[A, B] { self => | |
| def value: A | |
| def inverse: B |
| def foldMapF[F[_]: Monad, A, B](o: OptionT[F, A], f: A => B)(implicit M0: Monoid[B]): F[B] = o.fold(f, M0.zero) |
| import java.time.ZoneId | |
| import java.time.format.DateTimeFormatterBuilder | |
| import java.time.temporal.TemporalQueries | |
| def parseZoneId(input: String): ZoneId = | |
| new DateTimeFormatterBuilder() | |
| .appendZoneId | |
| .toFormatter | |
| .parse(input) | |
| .query(TemporalQueries.zoneId) |