feat: improve pitch datatype with sub-types for notes and octaves

Proj2.hs

@@ -12,14 +12,25 @@ where
 
 type GameState = ()
 
+data Note = A | B | C | D | E | F | G
+  deriving (Eq, Show, Ord)
+
+data Octave = One | Two | Three
+  deriving (Eq, Ord)
+
 data Pitch = Pitch
-  { note :: Char,
+  { note :: Note,
-    octave :: Int
+    octave :: Octave
   }
-  deriving (Eq)
+  deriving (Eq, Ord)
+
+instance Show Octave where
+  show One = "1"
+  show Two = "2"
+  show Three = "3"
 
 instance Show Pitch where
-  show (Pitch note octave) = note : show octave
+  show (Pitch note octave) = show note ++ show octave
 
 toPitch :: String -> Maybe Pitch
 toPitch _ = Just (Pitch 'A' 1)