Trying to start the applicative implementation of OptParser

GetOpt/Options.hs

@@ -1,7 +1,7 @@
 module GetOpt.Options where
 
-import GetOpt.Data(Option(..), OptionParser)
-import GetOpt.Parsers
+import GetOpt.Data( Option(..), OptionParser )
+import GetOpt.Parsers ( Parser(..) )
 
 meta :: String -> Mod a
 meta v = Mod $ \x -> x { metavar = v }

GetOpt/Parsers.hs

@@ -12,3 +12,11 @@ instance Functor Parser where
     fmap f (DefParser a) = DefParser $ f a
     fmap f (OptParser opt next) = OptParser (fmap (f .) opt) next
 
+instance Applicative Parser where
+    -- pure a -> f a
+    pure a = DefParser a
+
+    -- (<*>) f (a -> b) -> f a -> f b
+    (<*>) (DefParser f) p = fmap f p
+    -- (<*>) (OptParser (Option (a -> b -> c)) Parser (a -> b)) -> Parser a -> Parser c
+    (<*>) (OptParser f next) p = OptParser () next

Main.hs

@@ -17,19 +17,19 @@ getParser = Configuration
             <> meta "RULE"
             <> help "The rulset used." 
          )
-        --  <*> option (
-        --        long "start"
-        --     <> short 's'
-        --     <> meta "START"
-        --     <> help "At witch line should we start"
-        --     <> value 0
-        --  )
+         <*> option auto (
+               long "start"
+            <> short 's'
+            <> meta "START"
+            <> help "At witch line should we start"
+            <> value 0
+         )
 
 
 
 data Configuration = Configuration {
-    rule :: Int 
-    -- start :: Int,
+    rule :: Int,
+    start :: Int
     -- lines :: Maybe Int,
     -- window :: Int,
     -- move :: Int