eamelink · December 23, 2015 12:07 · Dec 23, 2015 · Dec 23, 2015
diff --git a/DisjunctionFilter.scala b/DisjunctionFilter.scala
@@ -21,6 +21,6 @@ object Test extends App{
     age <- 15.right[FailType] if age >= 18
   } yield age
 
-  println(result)
-  
+  println(result) // Prints -\/(FailType(too bad buddy!))
+
 }
diff --git a/DisjunctionFilter.scala b/DisjunctionFilter.scala
@@ -0,0 +1,26 @@
+import scalaz._
+import scalaz.Scalaz._
+
+object Test extends App{
+  trait Zero[A] {
+    def zero: A
+  }
+
+  implicit class RichDisjunction[A, B](value: A \/ B) {
+    def withFilter(p: B => Boolean)(implicit za: Zero[A]): A \/ B = value match {
+      case \/-(b) if !p(b) => -\/(za.zero)
+      case _ => value
+    }
+  }
+
+  case class FailType(msg: String)
+  implicit val zeroFailType = new Zero[FailType] { val zero = FailType("too bad buddy!") }
+
+
+  val result = for {
+    age <- 15.right[FailType] if age >= 18
+  } yield age
+
+  println(result)
+
+}