Kleisli Example 1

KleisliExample1.scala

import cats.data.Kleisli
import cats.implicits._

import scala.util.Try

case class Foo(i: Int)
case class Bar(f: Foo)

val makeFoo: String => Option[Foo] = (s: String) => Try(s.toInt).toOption.map(Foo)
val makeBar: Foo => Option[Bar]    = (f: Foo) => if (f.i < 0) None else Some(Bar(f))

val makeFooKleisli: Kleisli[Option, String, Foo] = Kleisli(makeFoo)
val makeBarKleisli: Kleisli[Option, Foo, Bar]    = Kleisli(makeBar)

val composed = makeFooKleisli andThen makeBarKleisli

composed.run("x")
composed.run("1")
composed.run("-1")