PeutEtre & Monad/Alternative for Parser

app/MyGetOpt.hs

@@ -6,7 +6,7 @@ instance Functor Parser where
     -- fmap :: (a -> b) -> f a -> f b
     fmap f p = P $ \x -> case parse p x of
                               Nothing -> Nothing
-                              Just (y, lo) -> Just $ (f y, lo)
+                              Just (y, lo) -> Just (f y, lo)
 
 instance Applicative Parser where
     -- pure :: a -> f a
@@ -17,14 +17,20 @@ instance Applicative Parser where
                                Nothing -> Nothing
                                Just (y, lo) -> parse (fmap y p) lo
 
+instance Monad Parser where
+    -- (>>=) :: forall a b. m a -> (a -> m b) -> m b
+    (>>=) p f = P $ \x -> case parse p x of
+                               Nothing -> Nothing
+                               Just (y, lo) -> parse (f y) lo
+
 instance Alternative Parser where
     -- empty :: f a
     empty = P (\x -> Nothing)
 
     -- (<|>) :: f a -> f a -> f a
-  --  (<|>) a b = P $ \x -> case parse a x of
+    (<|>) a b = P $ \x -> case parse a x of
-    --                           Nothing -> b
+                               Nothing -> parse b x
-      --                         _ -> a
+                               y -> y
 
 data Configuration = Configuration {
     rule :: Int,
@@ -40,4 +46,41 @@ defaultConfiguration = Configuration {
     Main.lines = Nothing,
     window = Just 80,
     move = Just 0
-}
+}
+
+--
+--data PeutEtre a = Juste a | Rien
+--
+--instance Functor PeutEtre where
+--    -- fmap :: (a -> b) -> f a -> f b
+--    fmap _ Rien = Rien
+--    fmap f (Juste x) = Juste $ f x
+--
+--instance Applicative PeutEtre where
+--    -- pure :: a -> f a
+--    pure x = Juste x
+--
+--    -- (<*>) :: f (a -> b) -> f a -> f b
+--    (<*>) _ Rien = Rien
+--    (<*>) Rien _ = Rien
+--    (<*>) (Juste f) (Juste x) = Juste $ f x
+--
+--instance Semigroup PeutEtre where
+--    -- (<>) :: a -> a -> a
+--    (<>) Rien x = x
+--    (<>) x _ = x
+--    (<>) Rien Rien = Rien
+--
+--instance Monad PeutEtre where
+--    -- (>>=) :: forall a b. m a -> (a -> m b) -> m b
+--    (>>=) Rien _ = Rien
+--    (>>=) (Juste x) f = f x
+--
+--instance Alternative PeutEtre where
+--    -- empty :: f a
+--    empty = Rien
+--
+--    -- (<|>) :: f a -> f a -> f a
+--    (<|>) (Juste a) _ = Juste a
+--    (<|>) _ (Juste a) = Juste a
+--    (<|>) _ _ = Rien