(implicit executor: ExecutionContext): Future[T] = ...
}
Future {
doExpensiveComputation()
}](https://image.slidesharecdn.com/implicits-berlin-160617084408/85/Implicits-Inspected-and-Explained-ScalaDays-2016-Berlin-6-320.jpg)
![Examples (2)
Collections
trait TraversableOnce[+A] {
def sum[B >: A](implicit num: Numeric[B]): B = ...
}
List(1,2,3).sum
res0: Int = 6](https://image.slidesharecdn.com/implicits-berlin-160617084408/85/Implicits-Inspected-and-Explained-ScalaDays-2016-Berlin-7-320.jpg)
![Examples (3)
Finagle
@implicitNotFound("Builder is not fully configured: Cluster: ${HasCluster}, Codec: ${HasCodec},
HostConnectionLimit: ${HasHostConnectionLimit}")
private[builder] trait ClientConfigEvidence[HasCluster, HasCodec, HasHostConnectionLimit]
class ClientBuilder[Req, Rep, HasCluster, HasCodec, HasHostConnectionLimit] private[finagle](...) {
def build()(
implicit THE_BUILDER_IS_NOT_FULLY_SPECIFIED_SEE_ClientBuilder_DOCUMENTATION:
ClientConfigEvidence[HasCluster, HasCodec, HasHostConnectionLimit]
): Service[Req, Rep] = ...
}
val builder: ClientBuilder[Request, Response, Yes, Yes, Nothing] =
ClientBuilder()
.codec(Http())
.hosts("twitter.com:80")
builder.build()
Error:(24, 15) Builder is not fully configured: Cluster: com.twitter.finagle.builder.ClientConfig.Yes,
Codec: com.twitter.finagle.builder.ClientConfig.Yes, HostConnectionLimit: Nothing
builder.build()
^](https://image.slidesharecdn.com/implicits-berlin-160617084408/85/Implicits-Inspected-and-Explained-ScalaDays-2016-Berlin-8-320.jpg)
![Typeclass uses
Ad-hoc polymorphism
Extension of libraries
trait Numeric[T] extends Ordering[T] {
def plus(x: T, y: T): T
def minus(x: T, y: T): T
def times(x: T, y: T): T
...
}](https://image.slidesharecdn.com/implicits-berlin-160617084408/85/Implicits-Inspected-and-Explained-ScalaDays-2016-Berlin-84-320.jpg)
Implicits Inspected and Explained @ ScalaDays 2016 Berlin
- 6. Examples Akka Futures trait ScalaActorRef def !(message: Any)(implicit sender: ActorRef = Actor.noSender): Unit = ... } actorRef ! SomeMessage("text") object Future { def apply[T](body: =>T)(implicit executor: ExecutionContext): Future[T] = ... } Future { doExpensiveComputation() }
- 7. Examples (2) Collections trait TraversableOnce[+A] { def sum[B >: A](implicit num: Numeric[B]): B = ... } List(1,2,3).sum res0: Int = 6
- 8. Examples (3) Finagle @implicitNotFound("Builder is not fully configured: Cluster: ${HasCluster}, Codec: ${HasCodec}, HostConnectionLimit: ${HasHostConnectionLimit}") private[builder] trait ClientConfigEvidence[HasCluster, HasCodec, HasHostConnectionLimit] class ClientBuilder[Req, Rep, HasCluster, HasCodec, HasHostConnectionLimit] private[finagle](...) { def build()( implicit THE_BUILDER_IS_NOT_FULLY_SPECIFIED_SEE_ClientBuilder_DOCUMENTATION: ClientConfigEvidence[HasCluster, HasCodec, HasHostConnectionLimit] ): Service[Req, Rep] = ... } val builder: ClientBuilder[Request, Response, Yes, Yes, Nothing] = ClientBuilder() .codec(Http()) .hosts("twitter.com:80") builder.build() Error:(24, 15) Builder is not fully configured: Cluster: com.twitter.finagle.builder.ClientConfig.Yes, Codec: com.twitter.finagle.builder.ClientConfig.Yes, HostConnectionLimit: Nothing builder.build() ^
- 11. Demo Implicit conversions (a.k.a. Implicit views) Implicit parameters Implicit classes Implicit declarations implicit def a2B(a : A) : B = ... def method(implicit x : Int) = ... implicit class X(y: Int) implicit val x = ...
- 84. Typeclass uses Ad-hoc polymorphism Extension of libraries trait Numeric[T] extends Ordering[T] { def plus(x: T, y: T): T def minus(x: T, y: T): T def times(x: T, y: T): T ... }