CIS 194 HW8

cis_194_hw8.hs

-- {-# OPTIONS_GHC -fno-warn-orphans #-}

module Party where

import Data.Semigroup
import Data.Tree
import Data.Function (on)
import Data.List (sortBy)

import Employee

-- Ex 1 - 4 (ex 2 skipped)

instance Semigroup GuestList where
  (<>) (GL e1 s1) (GL e2 s2) = GL (e1 ++ e2) (s1 + s2)

instance Monoid GuestList where
  mempty = GL [] 0

glCons :: Employee -> GuestList -> GuestList
glCons e@(Emp _ s) (GL es ss) = GL (e:es) (s + ss) 

moreFun :: GuestList -> GuestList -> GuestList
moreFun g1 g2 = if g1 > g2 then g1 else g2

treeFold :: (a -> [b] -> b) -> b -> Tree a -> b
treeFold f i (Node {rootLabel = r, subForest = s})
  = f r (map (treeFold f i) s) 

nextLevel :: Employee -> [(GuestList, GuestList)] -> (GuestList, GuestList)
nextLevel e@(Emp _ s)  [] = (GL [e] s, mempty)
nextLevel e xs = let right = map snd xs
                     best = map (uncurry moreFun) xs
                  in (glCons e $ mconcat right, mconcat best)

maxFun :: Tree Employee -> GuestList
maxFun t = uncurry moreFun $ treeFold nextLevel (mempty, mempty) t

-- Ex 5

sorted :: [Name] -> [Name]
sorted = sortBy (compare `on` (\n -> head $ words n))

readTree :: String -> Tree Employee
readTree = read

format :: GuestList -> String
format (GL es s) = "Total fun: " ++ show s ++ "\n" ++
                   (unlines . sorted $ map empName es)

main :: IO ()
main = do
  content <- readFile "Company.txt"
  let output = format . maxFun . readTree $ content
  putStrLn $ output