doubleMe x = x + x
doubleUs x y = doubleMe x + doubleMe y
doubleSmallNumber x = if x > 100 then x else x*2
boomBangs xs = [ if x < 10 then "BOOM!" else "BANG!" | x <- xs, odd x]
bmiTell :: (RealFloat a) => a -> a -> String
bmiTell weight height
| bmi <= skinny = "Underweight"
| bmi <= normal = "Normal"
| bmi <= fat = "Fat"
| otherwise = "Whale"
where bmi = weight / height ^ 2
skinny = 18.5
normal = 25.0
fat = 30.0
initials :: String -> String -> String
initials (f:_) (l:_) = [f] ++ ". " ++ [l] ++ "."
calcBmis :: (RealFloat a) => [(a, a)] -> [a]
calcBmis xs = [ w / h ^ 2 | (w, h) <- xs]
maximum' :: (Ord a) => [a] -> a
maximum' [] = error "비교할 항목이 없습니다"
maximum' [x] = x
maximum' (x:xs) = max x (maximum' xs)
{-maximum' [x,y] = if x > y then x else y-}
{-maximum' (x:xs) = if x > y then x else y-}
{-where y = maximum' xs-}
take' :: (Ord b, bum b) => b -> [a] -> [a]
{-take' n xs-}
{-| xs == [] = []-}
{-| n <= 0 = []-}
{-| otherwise = head xs:take (n-1) (tail xs)-}