"Hello, World!"
putStrLn "Hello, World!"
5 * 6 - 7
print $ 5 * 6 - 7
\x -> x * x $ 5 * 6 - 7
print $ \x -> x * x $ 5 * 6 - 7
[1,2,3,4]
print [1,2,3,4]
tail [1,2,3]
print $ tail [1,2,3]

print if 1 then '@' else '*'
-- if c == '\t' then '@' else c
\num -> num * num
\x -> x
3 + 4
4 * 5 - 1

firstNLines n cs = unlines $ take n $ lines cs

f1 = do { cs <- getContents ; print $ length $ lines cs }
f2 = print $ 5 + 2 * 5
f3 = print $ tail [1,2,3]
f4 = tail [1,2,3]

fib 0 = 0
fib 1 = 1
fib n = fib (n-1) + fib (n-2)

square n = n * n
triple a = a + a + a

main = putStrLn "Hello, World!"

main = print $ 5 * 6 - 7
-- main = print $ \x -> x * x $ 5 * 6 - 7