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trait Pointed[F[_]] { | |
def point[A](a: => A): F[A] | |
} | |
trait Functor[F[_]] { | |
def fmap[A, B](fa: F[A])(f: A => B): F[B] | |
} | |
trait Show[A] { | |
def shows(a: => A): String | |
} | |
trait OptionPointedInstances { | |
implicit def optionPoint: Pointed[Option] = new Pointed[Option] { | |
def point[A](a: => A) = Some(a) | |
} | |
} | |
trait OptionShowInstances extends OptionPointedInstances { | |
implicit def optionShow[A]: Show[Option[A]] = new Show[Option[A]] { | |
def shows(a: => Option[A]) = a.toString | |
} | |
} | |
trait OptionFunctorInstances extends OptionPointedInstances { | |
implicit def optionFunctor: Functor[Option] = new Functor[Option] { | |
def fmap[A, B](fa: Option[A])(f: A => B) = fa map f | |
} | |
} | |
object optionShowInstances extends OptionShowInstances | |
object optionFunctorInstances extends OptionFunctorInstances | |
object test { | |
import optionShowInstances._ | |
import optionFunctorInstances._ | |
def point[F[_], A](a: => A)(implicit F: Pointed[F]) = F.point(a) | |
point[Option, Int](1) | |
} |
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