SystemFw

cats-effect

The cats-effect project defines a purely functional effect type (IO[A]), and associated typeclasses defining its behaviour. The ones we care about for this example are:

trait Sync[F[_]] extends MonadError[F, Throwable] {
   def delay[A](a: => A): F[A]
   ...
}

neko-kai

package quantified

import cats.Monad

import scala.language.implicitConversions

/**
  * C[_] constraint applied to type F[_, _] quantified in first parameter, i.e.
  *
  * {{{

corenti13711539

  object Cached {
    def create[F[_]: Concurrent, A](fa: F[A], ttl: FiniteDuration)(implicit t: Timer[F]): F[Cached[F, A]] = {
      sealed trait State
      case class Value(v: A, ts: Long) extends State
      case class Updating(d: Deferred[F, Either[Throwable, A]]) extends State
      case object NoValue extends State
      def currentTimestamp = t.clock.monotonic(ttl.unit)

      Ref.of[F, State](NoValue).map { state =>
        new Cached[F, A] {