Basic functions
---------------
div, mod :: Integral a => a -> a -> a
even, odd :: Integral a => a -> Bool
(+), (*), (-), (/) :: Num a => a -> a -> a
(<), (<=), (>), (>=) :: Ord => a -> a -> Bool
(==), (/=) :: Eq a => a -> a -> Bool
(&&), (||) :: Bool -> Bool -> Bool
not :: Bool -> Bool
max, min :: Ord a => a -> a -> a
isAlpha, isAlphaNum, isLower, isUpper, isDigit :: Char -> Bool
toLower, toUpper :: Char -> Char
ord :: Char -> Int
chr :: Int -> Char


Library functions
-----------------
sum, product :: (Num a) => [a] -> a                 and, or :: [Bool] -> Bool
sum [1.0,2.0,3.0] = 6.0                             and [True,False,True] = False

product [1,2,3,4] = 24                              or [True,False,True] = True
maximum, minimum :: (Ord a) => [a] -> a             reverse :: [a] -> [a]
maximum [3,1,4,2] = 4                               reverse "goodbye" = "eybdoog"
minimum [3,1,4,2] = 1

concat :: [[a]] -> [a]                              (++) :: [a] -> [a] -> [a]
concat ["go","od","bye"] = "goodbye"                "good" ++ "bye" = "goodbye"

(!!) :: [a] -> Int -> a                             length :: [a] -> Int
[9,7,5] !! 1 = 7                                    length [9,7,5] = 3

head :: [a] -> a                                    tail :: [a] -> [a]
head "goodbye" = 'g'                                tail "goodbye" = "oodbye"

init :: [a] -> [a]                                  last :: [a] -> a
init "goodbye" = "goodby"                           last "goodbye" = 'e'

takeWhile :: (a->Bool) -> [a] -> [a]                take :: Int -> [a] -> [a]
takeWhile isLower "goodBye" = "good"                take 4 "goodbye" = "good"

dropWhile :: (a->Bool) -> [a] -> [a]                drop :: Int -> [a] -> [a]
dropWhile isLower "goodBye" = "Bye"                 drop 4 "goodbye" = "bye"

elem :: (Eq a) => a -> [a] -> Bool                  replicate :: Int -> a -> [a]
elem 'd' "goodbye" = True                           replicate 5 '*' = "*****"

zip :: [a] -> [b] -> [(a,b)]
zip [1,2,3,4] [1,4,9] = [(1,1),(2,4),(3,9)]