{-# Language RankNTypes, MultiParamTypeClasses #-}
module Data.Nonempty where

import Data.Functor.Identity
import Control.FIFO.FIFO
import Control.Unfoldable.Unfoldable
import Control.Traversable.Traversable

infixr 5 :|

data Nonempty a = a :| Nonempty a | End a deriving (Show,Eq, Ord)

--

instance Foldable0' Nonempty where
 foldMap0' = foldMap0'Default

instance Get0 Nonempty where
 get0 = get0Default

instance Unfoldable0 Nonempty

instance Set0 Nonempty where
 set0 = set0Default

instance Stream Nonempty

--

instance Foldable1' Nonempty where
 foldMap1' = foldMap1'Default

instance Get1 Nonempty where
 get1 (x :| xs) = (x,Just xs)
 get1 (End x)   = (x,Nothing)


instance Unfoldable1 Nonempty where
 unfoldr1 = unfoldr1Default

instance Set1 Nonempty where
 set1 (x,Just xs) = (x :| xs)
 set1 (x,Nothing) = (End x)

instance Traversable1' Nonempty where
 traverse1' = convert1

instance Linear Nonempty

instance Functor' Nonempty where
 fmap' = fmap'Default

instance Foldable' Nonempty where
 foldMap' = foldMap'Default

instance Traversable' Nonempty where
 traverse' = traverse'Default'

--

test :: Nonempty Int
test = unfoldr1 10 (\n -> if n == 0 then (n,Nothing) else (n,Just (n-1)))