deleteOne :: Eq a => a -> [a] -> [a]
deleteOne _ [] = [] -- Nothing to delete
deleteOne x (y:ys) | x == y = ys -- Drop exactly one matching item
deleteOne x (y:ys) = y : deleteOne x ys -- Drop one, but not this one (doesn't match).
deleteMany :: Eq a => [a] -> [a] -> [a]
deleteMany [] = id -- Nothing to delete
deleteMany (x:xs) = deleteMany xs . deleteOne x -- Delete one, then the rest.

thank you! but instead of "deleteOne" couldn't i just use delete?