mapN

src/main/scala/mycats/examples/ValidatedExample.scala

@@ -6,6 +6,7 @@ import mycats.examples.common.Utils.NonEmptyList
 import mycats.instances.ValidatedInstances.validatedApplicativeErrorInstance
 import mycats.lib.obj.Semigroup
 import mycats.lib.syntax.SemigroupalSyntax
+import mycats.lib.syntax.TupleCombineOps.Tuple2SemigroupalOps
 object ValidatedExample {
   type ValidatedNel[A] = Validated[NonEmptyList[String],A]
   val validatedNelInstance = validatedApplicativeErrorInstance[NonEmptyList[String],Long]
@@ -28,8 +29,12 @@ object ValidatedExample {
     validatedNelInstance.map(product)((Expense.apply _).tupled)
 
   }
+  private def mkExpenseMapN(id:Long,amount:Double):ValidatedNel[Expense] =
+    (expenseIdValidation(id), expenseAmountValidation(amount)).mapN((Expense.apply _).tupled)
+
+
   def main(args: Array[String]): Unit = {
-    val valid = mkExpense(-1,-12.0)
+    val valid = mkExpenseMapN(-1,-12.0)
     print(valid)
 
   }

src/main/scala/mycats/lib/syntax/TupleCombineOps.scala

@@ -0,0 +1,11 @@
+package mycats.lib.syntax
+import mycats.lib.morphisms.{Functor, Semigroupal}
+
+object TupleCombineOps {
+
+  implicit class Tuple2SemigroupalOps[F[_],A,B](ab:Tuple2[F[A],F[B]]){
+    def mapN[C](f:Tuple2[A,B]=>C)(implicit semigroupalWithFunctor:Semigroupal[F] with Functor[F]): F[C] =
+      semigroupalWithFunctor.map[(A,B),C](semigroupalWithFunctor.product[A,B](ab._1,ab._2))(f)
+  }
+
+}