override def run()

in algebird-core/src/main/scala/com/twitter/algebird/monad/StateWithError.scala [70:86]

• 17 lines of code
• 7 McCabe index (conditional complexity)

  override def run(state: S): Either[F, (S, U)] = {
    @annotation.tailrec
    def loop(inState: S, st: StateWithError[S, F, Any], stack: List[Any => StateWithError[S, F, Any]]): Any =
      st match {
        case StateFn(fn) =>
          fn(inState) match {
            case err @ Left(_) => err // bail at first error
            case noError @ Right((newState, out)) =>
              stack match {
                case head :: tailStack => loop(newState, head(out), tailStack)
                case Nil               => noError // recursion ends
              }
          }
        case FlatMappedState(st, next) => loop(inState, st, next :: stack)
      }
    loop(state, this, Nil).asInstanceOf[Either[F, (S, U)]]
  }