formatting is my passion

src/GoodList.hs

@@ -9,14 +9,14 @@ module GoodList (
 data GoodList a = Empty | Singleton a | Multiple a (GoodList a) a
 
 instance Functor GoodList where
-  fmap _ Empty = Empty
-  fmap f (Singleton a) = singleton $ f a
+  fmap _  Empty           = Empty
+  fmap f (Singleton a)    = singleton $ f a
   fmap f (Multiple a b c) = Multiple (f a) (fmap f b) (f c)
 
 instance Applicative GoodList where
   pure = singleton
-  Empty <*> _            = Empty
-  (Singleton f) <*> x    = fmap f x
+  Empty            <*> _ = Empty
+  (Singleton f)    <*> x = fmap f x
   (Multiple a b c) <*> x = append (append (fmap a x) (b <*> x)) (fmap c x)
 
 instance Semigroup (GoodList a) where
@@ -29,28 +29,28 @@ instance Show a => Show (GoodList a) where
   show x = "[" ++ show' x ++ "]"
     where
       show' :: Show a => GoodList a -> String
-      show' Empty = ""
-      show' (Singleton a) = show a
+      show' Empty                = ""
+      show' (Singleton a)        = show a
       show' (Multiple a Empty c) = show a ++ ", " ++ show c
-      show' (Multiple a b c) = show a ++ ", " ++ show' b ++ ", " ++ show c
+      show' (Multiple a b c)     = show a ++ ", " ++ show' b ++ ", " ++ show c
 
 
 singleton :: a -> GoodList a
 singleton = Singleton
 
 cons :: a -> GoodList a -> GoodList a
-cons x Empty = singleton x
-cons x (Singleton a) = Multiple x Empty a
+cons x  Empty           = singleton x
+cons x (Singleton a)    = Multiple x Empty a
 cons x (Multiple a b c) = Multiple x (a `cons` b) c
 
 snoc :: GoodList a -> a -> GoodList a
-snoc Empty = singleton
-snoc (Singleton a) = Multiple a Empty
+snoc  Empty           = singleton
+snoc (Singleton a)    = Multiple a Empty
 snoc (Multiple a b c) = Multiple a (b `snoc` c)
 
 append :: GoodList a -> GoodList a -> GoodList a
-append Empty ys                          = ys
-append (Singleton x) ys                  = cons x ys
-append xs Empty                          = xs
+append  Empty            ys              = ys
+append (Singleton x)     ys              = cons x ys
+append  xs               Empty           = xs
 append (Multiple a b c) (Singleton y)    = Multiple a (snoc b c) y
 append (Multiple a b c) (Multiple d e f) = Multiple a (snoc b c `append` cons d e) f

test/Main.hs

@@ -1,4 +1,8 @@
 module Main (main) where
+import GoodList
+
+abc :: GoodList Char
+abc = cons 'a' $ cons 'b' $ cons 'c' Empty
 
 main :: IO ()
-main = putStrLn "Test suite not yet implemented."
+main = print abc