Day2 use enum for shapes

src/Day2/Shared.hs

@@ -12,7 +12,7 @@ module Day2.Shared (
 ) where
 
 data Shape = Rock | Paper | Scissors
-  deriving (Show, Eq)
+  deriving (Show, Eq, Enum)
 
 newtype Score = Score Int
   deriving (Show, Eq)
@@ -36,9 +36,7 @@ newtype Game = Game (Shape, Shape)
   deriving (Show, Eq)
 
 shapeScore :: Shape -> Score
-shapeScore Rock = Score 1
-shapeScore Paper = Score 2
-shapeScore Scissors = Score 3
+shapeScore = Score . (+1) . fromEnum
 
 winAgainst :: Shape -> Shape
 winAgainst Rock = Paper

test/Day2Spec.hs

@@ -12,6 +12,13 @@ spec :: Spec
 spec =
   describe "Day2" $ do
     describe "Day2 - Shared" $ do
+      it "should implement winAgainst and loseAgainst for shapes" $ do
+        winAgainst Rock `shouldBe` Paper
+        winAgainst Paper `shouldBe` Scissors
+        winAgainst Scissors `shouldBe` Rock
+        loseAgainst Rock `shouldBe` Scissors
+        loseAgainst Paper `shouldBe` Rock
+        loseAgainst Scissors `shouldBe` Paper
       it "should have scores for shapes" $ do
         shapeScore Rock `shouldBe` Score 1
         shapeScore Paper `shouldBe` Score 2