smithy4s.capability.Contravariant.scala Maven / Gradle / Ivy
/*
* Copyright 2021-2024 Disney Streaming
*
* Licensed under the Tomorrow Open Source Technology License, Version 1.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://disneystreaming.github.io/TOST-1.0.txt
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package smithy4s.capability
/**
* Abstraction that encodes Contravariant Functors.
*/
trait Contravariant[F[_]] {
def contramap[A, B](fa: F[A])(f: B => A): F[B]
}
object Contravariant {
def apply[F[_]](implicit instance: Contravariant[F]): Contravariant[F] =
instance
implicit def contravariantOfCovariantInstance[F[_], G[_]](implicit
F: Covariant[F],
G: Contravariant[G]
): Contravariant[Wrapped[F, G, *]] = new Contravariant[Wrapped[F, G, *]] {
def contramap[A, B](fa: F[G[A]])(f: B => A): F[G[B]] =
F.map(fa)(ga => G.contramap(ga)(f))
}
}