Library functions implementation with fold (from LYAHFGG)

folds.hs

maximum' :: (Ord a) => [a] -> a  
maximum' = foldr1 (\x acc -> if x > acc then x else acc)  
  
reverse' :: [a] -> [a]  
reverse' = foldl (\acc x -> x : acc) []  
  
product' :: (Num a) => [a] -> a  
product' = foldr1 (*)  
  
filter' :: (a -> Bool) -> [a] -> [a]  
filter' p = foldr (\x acc -> if p x then x : acc else acc) []  
  
head' :: [a] -> a  
head' = foldr1 (\x _ -> x)  
  
last' :: [a] -> a  
last' = foldl1 (\_ x -> x)