module Data.Functor.Utils where

import Data.Monoid (class Monoid)
import Data.Semigroup (class Semigroup)
import Data.Ord (class Ord, max, min)
import Data.Maybe (Maybe(..))

newtype Max a = Max (Maybe a)
newtype Min a = Min (Maybe a)

getMax :: forall a. Max a -> Maybe a
getMax (Max a) = a

getMin :: forall a. Min a -> Maybe a
getMin (Min a) = a

instance Ord a => Semigroup (Max a) where
  append (Max Nothing) x = x
  append x (Max Nothing) = x
  append (Max (Just x)) (Max (Just y)) = 
    Max (Just (max x y))

instance Ord a => Monoid (Max a) where
  mempty = Max Nothing

instance Ord a => Semigroup (Min a) where
  append (Min Nothing) x = x
  append x (Min Nothing) = x
  append (Min (Just x)) (Min (Just y)) =
    Min (Just (min x y))

instance Ord a => Monoid (Min a) where
  mempty = Min Nothing