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module Party where
import Employee
import Data.Tree
-- Exercise 1
glCons :: Employee -> GuestList -> GuestList
glCons e@Emp { empFun = ef } (GL es cf) = GL (e:es) (cf + ef)
-- mappend (a.k.a. (<>)) has been moved to Semigroup
instance Semigroup GuestList where
(<>) (GL es1 f1) (GL es2 f2) = GL (es1 ++ es2) (f1 + f2)
instance Monoid GuestList where
mempty = GL [] 0
moreFun :: GuestList -> GuestList -> GuestList
moreFun gl1@(GL _ f1) gl2@(GL _ f2)
| f1 >= f2 = gl1
| otherwise = gl2
-- Exercise 2
treeFold :: (a -> [b] -> b) -> Tree a -> b
treeFold f (Node l subs) = f l $ map (\t -> treeFold f t) subs
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