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|
{-# LANGUAGE TypeFamilies #-}
module Main where
type family Elem c
class Col c where
isEmpty :: c -> Bool
add :: c -> Elem c -> c
headTail :: c -> (Elem c,c)
-- LIST
instance Col [a] where
isEmpty = null
add = flip (:)
headTail (x:xs) = (x,xs)
type instance Elem [a] = a
-- SEQUENCE
data Sequence a = Nil | Snoc (Sequence a) a deriving Show
instance Col (Sequence a) where
isEmpty Nil = True
isEmpty _ = False
add s x = Snoc s x
headTail (Snoc s x) = (x,s)
type instance Elem (Sequence a) = a
--
addAll c1 c2
| isEmpty c1
= c2
| otherwise
= let (x,c1') = headTail c1
in addAll c1' (add c2 x)
--
main = print $ addAll c1 c2
where c1 = ['a','b','c']
c2 = (Snoc (Snoc (Snoc Nil 'd') 'e') 'f')
|
