Add valueOr and merge to Validated, analog to Xor's

typelevel · Jun 14, 2016 · ef69db1 · ef69db1
1 parent b149835
commit ef69db1
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diff --git a/core/src/main/scala/cats/data/Validated.scala b/core/src/main/scala/cats/data/Validated.scala
@@ -27,6 +27,11 @@ sealed abstract class Validated[+E, +A] extends Product with Serializable {
    */
   def getOrElse[B >: A](default: => B): B = fold(_ => default, identity)
 
+  /**
+    * Return the Valid value, or the result of f if Invalid
+    */
+  def valueOr[B >: A](f: E => B): B = fold(f, identity)
+
   /**
    * Is this Valid and matching the given predicate
    */
@@ -203,6 +208,8 @@ sealed abstract class Validated[+E, +A] extends Product with Serializable {
     case Invalid(e) => Valid(e)
   }
 
+  def merge[EE >: E](implicit ev: A <:< EE): EE = fold(identity, ev.apply)
+
   /**
    * Ensure that a successful result passes the given predicate,
    * falling back to an Invalid of `onFailure` if the predicate

diff --git a/tests/src/test/scala/cats/tests/ValidatedTests.scala b/tests/src/test/scala/cats/tests/ValidatedTests.scala
@@ -114,6 +114,12 @@ class ValidatedTests extends CatsSuite {
     }
   }
 
+  test("valueOr consistent with swap then map then merge") {
+    forAll { (v: Validated[String, Int], f: String => Int) =>
+      v.valueOr(f) should === (v.swap.map(f).merge)
+    }
+  }
+
   test("toEither then fromEither is identity") {
     forAll { (v: Validated[String, Int]) =>
       Validated.fromEither(v.toEither) should === (v)