eff as an sbt dependency:
libraryDependencies += "org.atnos" %% "eff" % "4.3.1-20170420160654-e65dd5a" // to write types like Reader[String, ?] addCompilerPlugin("org.spire-math" %% "kind-projector" % "0.9.3")
To get types like Reader[String, ?] (with more than one type parameter) correctly inferred, you’ll need scala 2.12.1 with
scalacOptions += "-Ypartial-unification"
for 2.10.6 and 2.11.8, there’s a compiler plugin instead, use the full scala version as
addCompilerPlugin("com.milessabin" % "si2712fix-plugin_VERSION" % "1.2.0")
or you could use
scalaOrganization := "org.typelevel"
to get the
-Ypartial-unification flag for scala 2.11.8
If you want to use Scalaz as a library for functional programming you will also need:
libraryDependencies += "org.atnos" %% "eff-scalaz" % "4.3.1-20170420160654-e65dd5a"
This will allows you to use the
Eff monad as a Scalaz
Monad (instead of the cats
Monad which is the default implementation). The
eff-scalaz dependency is also necessary if you want to use scalaz
Task as an effect. (see Out of the box).
On the other hand if you prefer to use Monix
Task, you will need a dependency on
libraryDependencies += "org.atnos" %% "eff-monix" % "4.3.1-20170420160654-e65dd5a"
Fx are accessible in the
The functions used to create effects are grouped under different objects named after the effect type. For example if you want to create the
Eval effect you need to import:
You can also import most of the effects at once with:
The only effects not included in the previous import are:
Error effect. This effect requires a type parameter representing the “failure” type and must be provided by the user of the library
Future effect. This effect shares some operations like
runAsync with other “async” effects like monix’s
TaskEffect and the import could clash with
Interpreting effects usually requires some syntax to “run” a given effect. For example to “run” the
Option effect you will import:
// to create the effect import org.atnos.eff.option._ // to access the runOption method import org.atnos.eff.syntax.option._ fromOption(Option(1)).runOption
You can also access all the syntax imports at once with:
Intellij error highlighting doesn’t support implicit-directed type inference yet, check https://youtrack.jetbrains.com/issue/SCL-11140 or https://youtrack.jetbrains.com/issue/SCL-10753 for progress.
If you use Scalaz as your functional programming library you might need additional imports in order to use some creation methods specific to Scalaz. For example:
import org.atnos.eff.addon.scalaz.either._ fromDisjunction(\/-(1))
There is also an
all object importing all those methods at once:
import org.atnos.eff.addon.scalaz.all._ fromDisjunction(\/-(1))
And you can already guess, there are some syntax imports following the same pattern:
import org.atnos.eff.addon.scalaz.either._ import org.atnos.eff.addon.scalaz.syntax.either._ fromDisjunction(\/-(1)).runDisjunction