mini-zio.scala

final case class ZIO[-R, +E, +A](run: R => Either[E, A]) {
  final def map[B](f: A => B): ZIO[R, E, B] = 
    ZIO(r => run(r).map(f))

  final def flatMap[R1 <: R, E1 >: E, B](f: A => ZIO[R1, E1, B]): ZIO[R1, E1, B] = 
    ZIO(r => run(r).flatMap(a => f(a).run(r)))

  final def provide(r: R): ZIO[Any, E, A] = 
    ZIO(_ => run(r))

  final def either: ZIO[R, Nothing, Either[E, A]] = 
    ZIO(r => Right(run(r)))
}
object ZIO {
  def succeed[A](a: A): ZIO[Any, Nothing, A] = ZIO(_ => Right(a))
  def fail[E](e: E): ZIO[Any, E, Nothing] = ZIO(_ => Left(e))
  def environment[R]: ZIO[R, Nothing, R] = ZIO(r => Right(r))
  def effect[A](action: => A): ZIO[Any, Throwable, A] = ZIO { _ =>
    try Right(action) 
    catch { 
      case t : Throwable => Left(t)
    }
  }
}

to adhere better to the original, shouldn't access be environment ?

@pierangeloc Done, thank you!