import Data.Char
import Data.List


main :: IO()
main = do
  print $ task1 [(-1,1), (2,2), (0,-3)]
  print $ task2 "Hi how are you Today"
  print $ task3 8128
  print $ take 3 bonusTask3
  print $ task4 [1,2,1,3,1,4] 1
  print $ task5 [(0,1),(0,1),(0,1)] [True, False, True]
  print $ task6 [0,0,1,2,2,2,3,4]
  print $ task6' [0,0,1,2,2,2,3,4]


-- Task 1
task1 :: Ord a => [(a, a)] -> (a, a)
task1 ps = (minimum (map fst ps), maximum (map snd ps))


-- Task 2
task2 :: String -> Int
task2 str =
  length [word | word@(c:_) <- words str, isUpper c]


-- Task 3
task3 :: Int -> Bool
task3 n = n == sum [d | d <- [1..n-1], n `mod` d == 0]

bonusTask3 :: [Int]
bonusTask3 = filter task3 [1..]


-- Task 4
task4 :: Eq a => [a] -> a -> [Int]
task4 xs x = [i | (xi, i) <- zip xs [0..], xi == x]


-- Task 5
task5 :: [(a, a)] -> [Bool] -> [a]
task5 xs choice =
  map (\ ((f, s), c) -> if c then f else s) (zip xs choice)

task5' :: [(a, a)] -> [Bool] -> [a]
task5' xs choice =
  [if c then f else s | ((f, s), c) <- zip xs choice]


-- Task 6
task6 :: Eq a => [a] -> [a]
task6 xs = [x | (x:_) <- group xs]

task6' :: Eq a => [a] -> [a]
task6' =
  foldr (\ x rs -> if null rs then [x]
                   else if x == head rs then rs
                   else x : rs)
        []