--http://www.haskell.org/hoogle

{-

-}

doubleMe x = x + x
doubleUs x y = x * 2 + y * 2
doubleSmallNumber x = if x > 100
                    then "x"
                    else "y"
masa'koha' x = x

lucky :: Int -> String
lucky 7 = "LUCKY NUMBER SEVEN"
lucky x = "Sorry, you're out of luck, pal!"

factorial :: Int -> Int
factorial 0 = 1
factorial n = n * factorial (n - 1)

charName :: Char -> String
charName 'a' = "Albert"
charName 'b' = "Broseph"
charName n = "no match"

addVectors :: (Double, Double) -> (Double, Double) -> (Double, Double)
addVectors a b = (fst a + fst b, snd a + snd b)

head' :: [a] -> a
head' [] = error "Can't call head on an empty list,dummy!"
head' (x:_) = x

firstLetter :: String -> String
firstLetter "" = "Empty string"
firstLetter all@(x:xs) = "The first letter of " ++ all ++ " is " ++ [x]

bmiTell :: Double -> Double -> String
bmiTell weight height
    | bmi <= 18.5 =  "You're underweight, you emo, you!"
    | bmi <= 25.0 =  "You're supposedly normal.\\ Pffft, I bet you're ugly!"
    | bmi <= 30.0 =  "You're a fat,"
    | otherwise =  "You're a whale, congratulations!"
    where bmi = weight / height ^ 2

describeList :: [a] -> String
describeList ls = "The list is "
                  ++ case ls of [] -> "empty."
                                [x] -> "a singleton list."
                                xs -> "a longer list."