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Fix exercise 5.4 solution #208

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Fix exercise 5.4 solution #208

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20 changes: 12 additions & 8 deletions src/pages/monad-transformers/index.md
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Original file line number Diff line number Diff line change
Expand Up @@ -525,7 +525,7 @@ and launch devastating attacks.
The message sending method looks like this:

```scala
def getPowerLevel(autobot: String): Response[Int] =
def getPowerLevel(autobot: String)(implicit ec: ExecutionContext): Response[Int] =
???
```

Expand Down Expand Up @@ -590,11 +590,12 @@ val powerLevels = Map(
```
```scala mdoc:silent
import cats.instances.future._ // for Monad
import scala.concurrent.ExecutionContext
import scala.concurrent.ExecutionContext.Implicits.global

type Response[A] = EitherT[Future, String, A]

def getPowerLevel(ally: String): Response[Int] = {
def getPowerLevel(ally: String)(implicit ec: ExecutionContext): Response[Int] = {
powerLevels.get(ally) match {
case Some(avg) => EitherT.right(Future(avg))
case None => EitherT.left(Future(s"$ally unreachable"))
Expand Down Expand Up @@ -624,6 +625,7 @@ and use `map` and `flatMap` to combine the results:
import cats.implicits._
import cats.data._
import scala.concurrent.Future
import scala.concurrent.ExecutionContext
import scala.concurrent.ExecutionContext.Implicits.global

type Response[A] = EitherT[Future, String, A]
Expand All @@ -634,15 +636,15 @@ val powerLevels = Map(
"Hot Rod" -> 10
)

def getPowerLevel(ally: String): Response[Int] = {
def getPowerLevel(ally: String)(implicit ec: ExecutionContext): Response[Int] = {
powerLevels.get(ally) match {
case Some(avg) => EitherT.right(Future(avg))
case None => EitherT.left(Future(s"$ally unreachable"))
}
}
```
```scala mdoc:silent
def canSpecialMove(ally1: String, ally2: String): Response[Boolean] =
def canSpecialMove(ally1: String, ally2: String)(implicit ec: ExecutionContext): Response[Boolean] =
for {
power1 <- getPowerLevel(ally1)
power2 <- getPowerLevel(ally2)
Expand All @@ -655,7 +657,7 @@ takes two ally names and prints a message
saying whether they can perform a special move:

```scala mdoc:silent
def tacticalReport(ally1: String, ally2: String): String =
def tacticalReport(ally1: String, ally2: String)(implicit ec: ExecutionContext): String =
???
```

Expand All @@ -667,6 +669,7 @@ and `Await` and `fold` to unpack the `Future` and `Either`:
import cats.implicits._
import cats.data._
import scala.concurrent.Future
import scala.concurrent.ExecutionContext
import scala.concurrent.ExecutionContext.Implicits.global

type Response[A] = EitherT[Future, String, A]
Expand All @@ -677,7 +680,7 @@ val powerLevels = Map(
"Hot Rod" -> 10
)

def getPowerLevel(ally: String): Response[Int] = {
def getPowerLevel(ally: String)(implicit ec: ExecutionContext): Response[Int] = {
powerLevels.get(ally) match {
case Some(avg) => EitherT.right(Future(avg))
case None => EitherT.left(Future(s"$ally unreachable"))
Expand All @@ -686,16 +689,17 @@ def getPowerLevel(ally: String): Response[Int] = {
```
```scala mdoc:silent
import scala.concurrent.Await
import scala.concurrent.ExecutionContext
import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.duration._

def canSpecialMove(ally1: String, ally2: String): Response[Boolean] =
def canSpecialMove(ally1: String, ally2: String)(implicit ec: ExecutionContext): Response[Boolean] =
for {
power1 <- getPowerLevel(ally1)
power2 <- getPowerLevel(ally2)
} yield (power1 + power2) > 15

def tacticalReport(ally1: String, ally2: String): String = {
def tacticalReport(ally1: String, ally2: String)(implicit ec: ExecutionContext): String = {
val stack = canSpecialMove(ally1, ally2).value

Await.result(stack, 1.second) match {
Expand Down