import cats.implicits._
import cats.{Id, Monad}
trait KVStore[F[_], K, V] {
    def get(k: K): F[Option[V]]
    def put(k:K, v:V): F[Unit]
  }


class Dict[F[_]: Monad, K, V](store: KVStore[F, K, V]) {
    def computeIfAbsent(k: K, absent: => V): F[V] = {
      store.get(k).flatMap(opt => Monad[F].pure(opt.getOrElse(absent)))
    }
  }