Created
March 6, 2016 02:46
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import shims.{Permute2, Permute3} | |
import scalaz._ | |
object Scratch { | |
trait Functor[F[_]] { | |
def map[A, B](fa: F[A])(f: A => B): F[B] | |
} | |
object Functor { | |
def apply[F[_]](implicit F: Functor[F]) = F | |
implicit def listFunctor: Functor[List] = new Functor[List] { | |
def map[A, B](fa: List[A])(f: A => B): List[B] = fa map f | |
} | |
implicit def eitherFunctor[A]: Functor[A \/ ?] = new Functor[A \/ ?] { | |
def map[B, C](either: A \/ B)(f: B => C): A \/ C = either match { | |
case -\/(a) => -\/(a) | |
case \/-(b) => \/-(f(b)) | |
} | |
} | |
} | |
trait Unapply[E, TC[_[_]]] { | |
type A | |
type F[A] | |
def tc: TC[F] | |
def apply(e: E): F[A] | |
} | |
object Unapply { | |
type Aux[E, TC[_[_]], F0[_], A0] = Unapply[E, TC] { type A = A0; type F[A] = F0[A] } | |
implicit def materialize1[F0[_], TC[_[_]], A0](implicit tc0: TC[F0]): Unapply.Aux[F0[A0], TC, F0] = new Unapply[F0[A0], TC] { | |
type A = A0 | |
type F[A] = F0[A] | |
def tc = tc0 | |
def apply(e: F0[A]): F0[A] = e | |
} | |
implicit def materialize2[F01[_, _], F02[_, _], Z, TC[_[_]], A](implicit ev: Permute2[F01, F02], tc0: TC[F02[Z, ?]]): Unapply.Aux[F02[Z, A], TC, F02[Z, ?]] = new Unapply[F02[Z, A], TC] { | |
type F[A] = F02[Z, A] | |
def tc = tc0 | |
} | |
implicit def materialize3[F01[_, _, _], F02[_, _, _], Y, Z, TC[_[_]], A](implicit ev: Permute3[F01, F02], tc0: TC[F02[Y, Z, ?]]): Unapply.Aux[F02[Y, Z, A], TC, F02[Y, Z, ?]] = new Unapply[F02[Y, Z, A], TC] { | |
type F[A] = F02[Y, Z, A] | |
def tc = tc0 | |
} | |
} | |
def bar[E](fa: E)(implicit U: Unapply[E, Functor]) = U.tc.map(U(fa)) { _.hashCode } | |
// examples follow | |
bar(List(1, 2, 3)) | |
val e: String \/ Int = \/-(42) | |
bar(e) | |
} |
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