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Use ContextShift.apply in the tutorial #489

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Apr 9, 2019
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Use ContextShift.apply in the tutorial #489

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12 changes: 4 additions & 8 deletions site/src/main/tut/tutorial/tutorial.md
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Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,7 @@ version := "1.0"

scalaVersion := "2.12.8"

libraryDependencies += "org.typelevel" %% "cats-effect" % "1.0.0" withSources() withJavadoc()
libraryDependencies += "org.typelevel" %% "cats-effect" % "1.2.0" withSources() withJavadoc()

scalacOptions ++= Seq(
"-feature",
Expand Down Expand Up @@ -1139,13 +1139,11 @@ import cats.effect._
import cats.implicits._
import scala.concurrent.ExecutionContext

def doHeavyStuffInADifferentThreadPool[F[_]: ContextShift: Sync](implicit ec: ExecutionContext): F[Unit] = {
val csf = implicitly[ContextShift[F]]
def doHeavyStuffInADifferentThreadPool[F[_]: ContextShift: Sync](implicit ec: ExecutionContext): F[Unit] =
for {
_ <- csf.evalOn(ec)(Sync[F].delay(println("Hi!"))) // Swapping to thread pool of given ExecutionContext
_ <- ContextShift[F].evalOn(ec)(Sync[F].delay(println("Hi!"))) // Swapping to thread pool of given ExecutionContext
_ <- Sync[F].delay(println("Welcome!")) // Running back in default thread pool
} yield ()
}
```

#### Exercise: using a custom thread pool in echo server
Expand All @@ -1164,11 +1162,9 @@ connected client. So the beginning of the `echoProtocol` function would look lik
```scala
def echoProtocol[F[_]: Sync: ContextShift](clientSocket: Socket, stopFlag: MVar[F, Unit])(implicit clientsExecutionContext: ExecutionContext): F[Unit] = {

val csf = implicitly[ContextShift[F]]

def loop(reader: BufferedReader, writer: BufferedWriter, stopFlag: MVar[F, Unit]): F[Unit] =
for {
lineE <- csf.evalOn(clientsExecutionContext)(Sync[F].delay(reader.readLine()).attempt)
lineE <- ContextShift[F].evalOn(clientsExecutionContext)(Sync[F].delay(reader.readLine()).attempt)
// ...
```

Expand Down