smithy4s.capability.Covariant.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
import smithy4s.kinds.PolyFunction
/**
* Abstraction that encodes Functors
*/
trait Covariant[F[_]] {
def map[A, B](fa: F[A])(f: A => B): F[B]
}
object Covariant {
def apply[F[_]](implicit instance: Covariant[F]): Covariant[F] = instance
def liftPolyFunction[F[_]] = new PartiallyAppliedLiftK[F]()
class PartiallyAppliedLiftK[F[_]](private val dummy: Boolean = true)
extends AnyVal {
def apply[G1[_], G2[_]](fk: PolyFunction[G1, G2])(implicit
F: Covariant[F]
): PolyFunction[Wrapped[F, G1, *], Wrapped[F, G2, *]] =
new PolyFunction[Wrapped[F, G1, *], Wrapped[F, G2, *]] {
def apply[A](fa: F[G1[A]]): F[G2[A]] = F.map(fa)(fk(_))
}
}
}