Esempio di Either Monad

scala/src/main/scala/org/gym/fp/BooleanResult.scala

@@ -0,0 +1,27 @@
+package org.gym.fp
+
+// data type
+sealed trait BooleanResult[+A] {
+
+  def map[B](f: A => B): BooleanResult[B]
+
+  def flatMap[B](f: A => BooleanResult[B]): BooleanResult[B]
+
+}
+
+// data constructor
+case class TrueResult[A](value: A) extends BooleanResult[A] {
+
+  override def map[B](f: A => B): BooleanResult[B] = TrueResult(f(value))
+
+  override def flatMap[B](f: A => BooleanResult[B]): BooleanResult[B] = f(value)
+
+}
+
+case class FalseResult[A]() extends BooleanResult[A] {
+
+  override def map[B](f: A => B): BooleanResult[B] = FalseResult()
+
+  override def flatMap[B](f: A => BooleanResult[B]): BooleanResult[B] = FalseResult()
+
+}

scala/src/main/scala/org/gym/fp/EitherExample.scala

@@ -0,0 +1,22 @@
+package org.gym.fp
+
+case class Failed(msg: String)
+
+object EitherExample extends App {
+
+  println(giveMeAnAnswer(divideXByY(1, 0)))
+  println(giveMeAnAnswer(divideXByY(1, 1)))
+
+  def divideXByY(x: Int, y: Int): Either[String, Int] = {
+    if (y == 0) Left("Dude, can't divide by 0") else Right(x / y)
+  }
+
+  private def giveMeAnAnswer(question: Either[String, Int]): String = {
+    question match {
+      case Left(value) => "Answer: " + value
+      case Right(value) => "Answer: " + value
+      case _ => "I don't known"
+    }
+  }
+
+}