programaker · November 8, 2021 17:38 · Nov 8, 2021
diff --git a/align.scala b/align.scala
@@ -0,0 +1,70 @@
+import scala.util.Try
+import cats.Functor
+import cats.Align
+import cats.data.Ior
+
+type Decimal = Int
+type Roman = String
+
+def f[F[_]: Align: Functor](fi: F[Decimal], fs: F[Roman]): F[String] =
+  import cats.syntax.align.* // <- HERE
+  import cats.syntax.functor.*
+
+  // `align` is like a "zip on steroids"!
+  // It pairs 2 effects regardless whether they are symmetric or not
+  // i.e they have the same size, they are both defined, they are both successful, etc.
+  //
+  // The `Align` typeclass provides more interesting "zippers" like this.
+  // Check them out! https://typelevel.org/cats/api/cats/Align.html
+  fi.align(fs).map { ior =>
+    ior match
+      case Ior.Both(decimal, roman) => s"$decimal is $roman in Roman"
+      case Ior.Left(decimal)        => s"$decimal has no Roman"
+      case Ior.Right(roman)         => s"$roman has no Decimal"
+  }
+
+///
+
+val decimals1 = List(1, 2, 3, 0)
+val romans1 = List("I", "II", "III")
+val out1 = f(decimals1, romans1)
+// List[String] = List(1 is I in Roman, 2 is II in Roman, 3 is III in Roman, 0 has no Roman)
+
+val decimals2 = List(1, 2, 3)
+val romans2 = List("I", "II", "III", "IV")
+val out1a = f(decimals2, romans2)
+// List[String] = List(1 is I in Roman, 2 is II in Roman, 3 is III in Roman, IV has no Decimal)
+
+val out1b = f(List.empty, List.empty)
+// List[String] = List()
+
+///
+
+import cats.syntax.option.*
+
+val out2 = f(0.some, None)
+// Option[String] = Some(1 is I in Roman)
+
+val out2a = f(1.some, "I".some)
+// Option[String] = Some(1 is I in Roman)
+
+val out2b = f(None, "X".some)
+// Option[String] = Some(X has no Decimal)
+
+val out2c = f(None, None)
+
+///
+
+type Either_[A] = Either[String, A]
+
+val out3 = f(Right(1), Left("ERROR"))
+// Either[String, String] = Right(1 has no Roman)
+
+val out3a = f[Either_](Right(1), Right("I"))
+// Either[String, String] = Right(1 is I in Roman)
+
+val out3b = f(Left("ERROR"), Right("X"))
+// Either[String, String] = Right(X has no Decimal)
+
+val out3c = f[Either_](Left("ERROR"), Left("ERROR"))
+// Either[String, String] = Left(ERROR)