Convert the following Haskell expression using do notation to the equivalent non-do form using the Monad operator >>=.

do args <- getArgs
   fstr <- readFile (head args)
   putStrLn (show (length fstr))

Convert the following Haskell expression using do notation to the equivalent non-do form using the Monad operator >>=.

do a <- getLine
   b <- getLine
   putStrLn b
   putStrLn a

Write a function main with type IO () which reads two lines from the user and then displays them back in opposite order (the second line, then the first line).

Write a function readLines of type IO [String] that reads lines typed by the user until the user types “.” and then returns a list of the lines typed wrapped in an IO, not including the “.” line. You will use the getLine function (of type IO String) to read a single line.

Define a Haskell function skipToLine whose type signature is as below.

skipToLine :: Int -> IO String

Given a positive integer, skipToLine should read that many lines from the user using the getLine function of type IO String, and its result should be the IO String packaged in the final call to getLine.

Complete the following class definition by writing the >>= function for the Maybe type.

data Maybe a = Just a | Nothing
instance Monad (Maybe a) where
    return x        =  Just x

For this type, the expression x >>= f should yield Just (f data) if x is Just data, and it should yield Nothing if x is Nothing.

Based on the BNF grammar below, draw a syntax tree for the sentence a a x b x b x.

S

→

a S b S | x

Based on the BNF grammar below, draw a syntax tree for the sentence a b c a c b a b.

S	→	a T b | c
T	→	b S S a | S

Using BNF syntax, write a context-free grammar for the language of zero or more a's listed separated by commas, but without beginning or ending in a comma. The four shortest strings in the language are the empty string, “a”, “a,a”, “a,a,a”.