Tagless Final example in Scala + Cats

tf.sc

import scala.language.higherKinds
import cats._
import cats.implicits._

final case class User(id: Integer, name: String, age: Integer, isAdmin: Boolean)

val fakeUsers: List[User] = List(
  User(1, "John Connor", 32, false),
  User(2, "John Smith", 18, false),
  User(3, "Mark Brian", 28, false)
)

trait UserOps[F[_]] {
  def search(name: String): F[List[User]]
  def makeAdmin(users: List[User]): F[List[User]]
  def save(users: List[User]): F[List[Boolean]]
}

object identityInterpreter extends UserOps[Id] {
  def search(name: String): Id[List[User]] =
    fakeUsers.filter(u => u.name contains name)
  def makeAdmin(users: List[User]): Id[List[User]] =
    users.map(u => u.copy(isAdmin = true))
  def save(users: List[User]): Id[List[Boolean]] = users.map(_.isAdmin)
}

def program[F[_]: Monad](F: UserOps[F]) =
  for {
    johns <- F.search("John")
    admins <- F.makeAdmin(johns)
    res <- F.save(admins)
  } yield res

print(program(identityInterpreter))