Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Slight clean up of State docs #2226

Merged
merged 1 commit into from
Apr 13, 2018
Merged

Slight clean up of State docs #2226

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
12 changes: 6 additions & 6 deletions docs/src/main/tut/datatypes/state.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -196,7 +196,7 @@ This may seem surprising, but keep in mind that `b` isn't simply a `Boolean`. It
## Interleaving effects

Let's expand on the above example; assume that our random number generator works asynchronously by fetching results from a remote server:
```tut:book
```tut:silent
import scala.concurrent.Future
import scala.concurrent.ExecutionContext.Implicits.global
Expand Down Expand Up @@ -228,7 +228,7 @@ The `seed` that `State.apply` passes in is now a `Future`, so we must map it. Bu
Luckily, `State[S, A]` is an alias for `StateT[Eval, S, A]` - a monad transformer defined as `StateT[F[_], S, A]`. This data type represents computations of the form `S => F[(S, A)]`.

If we plug in our concrete types, we get `AsyncSeed => Future[(AsyncSeed, A)]`, which is something we can work with:
```tut:book
```tut:silent
import cats.data.StateT
import cats.instances.future._
import scala.concurrent.ExecutionContext.Implicits.global
Expand All @@ -250,7 +250,7 @@ It should be noted that different combinators on `StateT` impose different const
## Changing States

More complex, stateful computations cannot be easily modeled by a single type. For example, let's try to model a door's state:
```tut:book
```tut:silent
sealed trait DoorState
case object Open extends DoorState
case object Closed extends DoorState
Expand All @@ -262,8 +262,8 @@ def close: State[DoorState, Unit] = ???
```

We would naturally expect that `open` would only operate on doors that are `Closed`, and vice-versa. However, to implement these methods currently, we have to pattern-match on the state:
```tut:book
def open: State[DoorState, Unit] = State { doorState =>
```tut:silent
val open: State[DoorState, Unit] = State { doorState =>
doorState match {
case Closed => (Open, ())
case Open => ??? // What now?
Expand All @@ -278,7 +278,7 @@ The most elegant solution would be to model this requirement statically using ty
This data type models a stateful computation of the form `SA => F[(SB, A)]`; that's a function that receives an initial state of type `SA` and results in a state of type `SB` and a result of type `A`, using an effect of `F`.

So, let's model our typed door:
```tut:book
```tut:silent
import cats.Eval
import cats.data.IndexedStateT
Expand Down
2 changes: 1 addition & 1 deletion project/plugins.sbt
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -13,4 +13,4 @@ addSbtPlugin("org.xerial.sbt" % "sbt-sonatype" % "2.0")
addSbtPlugin("com.47deg" % "sbt-microsites" % "0.7.17")
addSbtPlugin("com.dwijnand" % "sbt-travisci" % "1.1.1")
addSbtPlugin("org.lyranthe.sbt" % "partial-unification" % "1.1.0")
addSbtPlugin("org.tpolecat" % "tut-plugin" % "0.6.3")
addSbtPlugin("org.tpolecat" % "tut-plugin" % "0.6.4")