smithy4s.capability.Covariant.scala Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of smithy4s-core_sjs1_3 Show documentation

core

There is a newer version: 0.19.0-41-91762fb

/*
 *  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(_))
      }
  }

}