feat: implement toPitch

Proj2.hs

@@ -33,7 +33,29 @@ instance Show Pitch where
   show (Pitch note octave) = show note ++ show octave
 
 toPitch :: String -> Maybe Pitch
-toPitch _ = Just (Pitch 'A' 1)
+toPitch [note, octave] = Pitch <$> charToNote note <*> charToOctave octave
+  where
+    charToNote :: Char -> Maybe Note
+    charToNote c =
+      lookup
+        c
+        [ ('A', A),
+          ('B', B),
+          ('C', C),
+          ('D', D),
+          ('E', E),
+          ('F', F),
+          ('G', G)
+        ]
+    charToOctave :: Char -> Maybe Octave
+    charToOctave c =
+      lookup
+        c
+        [ ('1', One),
+          ('2', Two),
+          ('3', Three)
+        ]
+toPitch _ = Nothing
 
 feedback :: [Pitch] -> [Pitch] -> (Int, Int, Int)
 feedback _ _ = (0, 0, 0)