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SyncEffect.scala
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SyncEffect.scala
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/*
* Copyright (c) 2017-2021 The Typelevel Cats-effect Project Developers
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* 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 cats
package effect
import cats.data.{EitherT, WriterT}
import scala.annotation.implicitNotFound
/**
* A monad that can suspend side effects into the `F` context and
* that supports only synchronous lazy evaluation of these effects.
*/
@implicitNotFound("Could not find an instance of SyncEffect for ${F}")
trait SyncEffect[F[_]] extends Sync[F] {
/**
* Convert to any other type that implements `Sync`.
*/
def runSync[G[_], A](fa: F[A])(implicit G: Sync[G]): G[A]
/**
* [[SyncEffect.runSync]] as a natural transformation.
*/
def runSyncK[G[_]](implicit G: Sync[G]): F ~> G = new (F ~> G) {
def apply[A](fa: F[A]): G[A] = runSync[G, A](fa)
}
}
object SyncEffect {
/**
* [[SyncEffect]] instance built for `cats.data.EitherT` values initialized
* with any `F` data type that also implements `SyncEffect`.
*/
implicit def catsEitherTSyncEffect[F[_]: SyncEffect]: SyncEffect[EitherT[F, Throwable, *]] =
new EitherTSyncEffect[F] { def F = SyncEffect[F] }
/**
* [[SyncEffect]] instance built for `cats.data.WriterT` values initialized
* with any `F` data type that also implements `SyncEffect`.
*/
implicit def catsWriterTSyncEffect[F[_]: SyncEffect, L: Monoid]: SyncEffect[WriterT[F, L, *]] =
new WriterTSyncEffect[F, L] { def F = SyncEffect[F]; def L = Monoid[L] }
private[effect] trait EitherTSyncEffect[F[_]]
extends SyncEffect[EitherT[F, Throwable, *]]
with Sync.EitherTSync[F, Throwable] {
protected def F: SyncEffect[F]
def runSync[G[_], A](fa: EitherT[F, Throwable, A])(implicit G: Sync[G]): G[A] =
F.runSync(F.rethrow(fa.value))
}
private[effect] trait WriterTSyncEffect[F[_], L] extends SyncEffect[WriterT[F, L, *]] with Sync.WriterTSync[F, L] {
protected def F: SyncEffect[F]
protected def L: Monoid[L]
def runSync[G[_], A](fa: WriterT[F, L, A])(implicit G: Sync[G]): G[A] =
F.runSync(F.map(fa.run)(_._2))
}
/**
* Summon an instance of [[SyncEffect]] for `F`.
*/
@inline def apply[F[_]](implicit instance: SyncEffect[F]): SyncEffect[F] = instance
trait Ops[F[_], A] {
type TypeClassType <: SyncEffect[F]
def self: F[A]
val typeClassInstance: TypeClassType
def runSync[G[_]](implicit G: Sync[G]): G[A] = typeClassInstance.runSync[G, A](self)(G)
}
trait AllOps[F[_], A] extends Ops[F, A] with Sync.AllOps[F, A] {
type TypeClassType <: SyncEffect[F]
}
trait ToSyncEffectOps {
implicit def toSyncEffectOps[F[_], A](target: F[A])(implicit tc: SyncEffect[F]): Ops[F, A] {
type TypeClassType = SyncEffect[F]
} = new Ops[F, A] {
type TypeClassType = SyncEffect[F]
val self: F[A] = target
val typeClassInstance: TypeClassType = tc
}
}
object nonInheritedOps extends ToSyncEffectOps
object ops {
implicit def toAllSyncEffectOps[F[_], A](target: F[A])(implicit tc: SyncEffect[F]): AllOps[F, A] {
type TypeClassType = SyncEffect[F]
} = new AllOps[F, A] {
type TypeClassType = SyncEffect[F]
val self: F[A] = target
val typeClassInstance: TypeClassType = tc
}
}
}