Added haskell implementation with monads

Author: DzyubSpirit

Haskell/insane/DoubleLinked.hs

@@ -0,0 +1,53 @@
+module DoubleLinked where
+
+import Control.Monad
+import Prelude hiding (fromList)
+
+import SingleLinked as L hiding (fromList)
+
+data DList a = DList {
+  getDirect  :: List a,
+  getInverse :: List a
+}
+
+instance Functor DList where
+  fmap f (DList dir inv) = DList (appF dir) (appF inv)
+    where appF = fmap f
+
+empty :: DList a
+empty = DList Empty Empty
+
+push :: a -> DList a -> DList a
+push el list = list {
+  getDirect  = addToEnd el $ getDirect list,
+  getInverse = el :+: getInverse list
+}
+
+pop :: DList a -> (a, DList a)
+pop (DList Empty Empty)     = error "pop on empty list"
+pop (DList Empty _    )     = error "wrong structured list"
+pop (DList _     Empty)     = error "wrong structured list"
+pop (DList dir (el:+:rest)) = (el, DList (L.init dir) rest)
+
+fromList :: [a] -> DList a
+fromList = foldl (flip push) empty
+
+node :: a -> DList a
+node = (`push` empty)
+
+main = do
+  let list3 = Human <$> fromList ["first", "second", "third"]
+      printPop list = let (el, list') = pop list
+                      in print el >> return list'
+      nPrintPop n = foldr (>=>) return 
+                  $ replicate n printPop
+      pushHuman name = return . push (Human name)
+  foldr (>=>) return [
+      nPrintPop 3,
+      pushHuman "uno",
+      pushHuman "due",
+      printPop,
+      pushHuman "tre",
+      nPrintPop 2
+    ] list3  
+  return ()

Haskell/insane/SingleLinked.hs

@@ -0,0 +1,41 @@
+module SingleLinked
+  ( List(..)
+  , Human(..)
+  , addToEnd
+  , init
+  , fromList
+  ) where
+
+import Prelude hiding (init, fromList)
+
+data List a = a :+: List a
+            | Empty
+  deriving (Show)
+infixr :+:
+
+instance Functor List where
+  fmap f Empty = Empty
+  fmap f (x :+: xs) = f x :+: fmap f xs
+
+data Human = Human {
+  getName :: String
+} deriving (Show)
+
+addToEnd :: a -> List a -> List a
+addToEnd el Empty    = el :+: Empty
+addToEnd el (x:+:xs) = x :+: addToEnd el xs
+
+init :: List a -> List a
+init Empty         = error "init on empty list"
+init (x :+: Empty) = Empty
+init (x :+: xs)    = x :+: init xs
+
+fromList :: [a] -> List a
+fromList = foldr (:+:) Empty
+
+main = do
+  let (n1 :+: n2 :+: n3 :+: _) = fmap Human . fromList
+                               $ ["first", "second", "third"]
+  print n1
+  print n2
+  print n3