1 object Dependencies { 2  trait PasswordControl { 3  val mapPasswords: Map[String,String] 4  def matchUserPassword(uid: String, pwd: String): Boolean 5  } 6 }

 1 object catsComposeFree extends App {  2  import Dependencies._  3  import FreeModules._  4  import DSLs._  5  import IMPLs._  6   object UserPasswords extends PasswordControl {  7     override val mapPasswords: Map[String, String] = Map(  8       "Tiger" -> "123",  9       "John" -> "456"
10  ) 11     override def matchUserPassword(uid: String, pwd: String): Boolean =
12       mapPasswords.getOrElse(uid,pwd+"!") == pwd 13  } 14 
15   val r = interactLoginDSL.foldMap(userLogin).run(UserPasswords) 16  println(r) 17 
18 }

 1 Enter your User ID:  2 Tiger  3 Enter your Password:  4 123
 5 true
 6 ...  7 Enter your User ID:  8 Chan  9 Enter your Password: 10 123
11 false

1     val userLoginDSL: Free[InteractLogin,Unit] = for { 2       uid <- ask[InteractLogin]("Enter your User ID:") 3       pwd <- ask[InteractLogin]("Enter your Password:") 4       aut <- authenticate[InteractLogin](uid,pwd) 5       _ <- if (aut) tell[InteractLogin](s"Hello $uid") 6            else tell[InteractLogin]("Sorry, who are you?") 7     } yield()

1   //val r = interactLoginDSL.foldMap(userLogin).run(UserPasswords) 2   //println(r)
3   userLoginDSL.foldMap(userLogin).run(UserPasswords)

 1 Enter your User ID:  2 Tiger  3 Enter your Password:  4 123
 5 Hello Tiger  6 ...  7 Enter your User ID:  8 CHAN  9 Enter your Password: 10 123
11 Sorry, who are you?

1     sealed trait Auth[+A] 2     object Auth { 3       case class Authorize(uid: String) extends Auth[Boolean] 4       def authorize[G[_]](uid:String)(implicit I: Inject[Auth,G]): Free[G,Boolean] =
5  Free.liftF(I.inj(Authorize(uid))) 6     }

 1 object Dependencies {  2  trait PasswordControl {  3  val mapPasswords: Map[String,String]  4  def matchUserPassword(uid: String, pwd: String): Boolean  5  }  6  trait PermControl {  7  val mapAuthorized: Map[String,Boolean]  8  def authorized(uid: String): Boolean  9  } 10 }