module.frea

magic = "Hello From Another Module"

data Maybe a
  = Nothing
  | Just a


data IMaybe
  = INothing
  | IJust Int


data Either a b
  = Left a
  | Right b

data Oneof a b c
  = A a
  | B b
  | C c


data Wrong a b -- (a :: * -> *) (b :: *)
  = One (a b)
  | Two b

data Worse a -- (a :: * -> *)
  = First (a Int)

-- (First (Left 23)) :: forall a . Worse (Either Int) a
-- tohle nedava smysl
-- Either Int neni type, chybi tam dalsi parametr
-- absolutne nechapu kam se jako ztratil
-- 
-- ale podle GHC je to spravne

data Bad a -- (a :: * -> * -> *)
  = Ba (a Int Char)

data Boo a b c = Bo (a b c)

data Coo a = Co a


data Malformed b = Con (Either b)


data Experiment
  = Try [Int]


data IList
  = Nil
  | Int ::: IList


showIList list = (which-IList list
                    "Nil"
                    ( \ head tail -> ( ((show head) ++ " ::: ") ++ (showIList tail) ) ))


showMaybe maybe = (which-IMaybe maybe
                    "Nothing"
                    (\ v -> ("Just " ++ ((#show) v)) ))


ihead lst =  (which-IList lst
              INothing
              (\ h t -> (IJust h)))


imap fn lst =  (which-IList lst
                Nil
                (\ h t -> ((fn h) ::: (imap fn t))))


sum ilist = (which-IList ilist
              0
              (\ head tail -> (head + (sum tail))))


itake n lst = if (n == 0) then Nil else 
                                    (which-IList lst
                                      Nil
                                      (\ h t -> (h ::: (itake (n - 1) t)))
                                    )


-- some examples

ones = (1 ::: ones)

list = (1 ::: (2 ::: (3 ::: (4 ::: (5 ::: Nil)))))

double n = (n * 2)


iif bool thenn elsee = (which-Boolean bool
                        thenn
                        elsee)


fact n = if (n == 0) then 1 else (n * (fact (n - 1)))


mayAdd n maybe = (which-IMaybe maybe
                  INothing
                  (\ v -> (IJust (v + n))))