Test 2 Review B

[1] [2] [3] [4] [5] [6] [7] [8] [9]

Problem R2b.1.

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))

getArgs >>= (\args -> readFile (head args)

                        >>= \fstr -> putStrLn (show (length fstr)))

Problem R2b.2.

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

getLine >>= (\a -> getLine >>= (\b putStrLn second >> putStrLn a))

Problem R2b.3.

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).

main = do first <- getLine

          second <- getLine

          putStrLn second

          putStrLn first

Problem R2b.6.

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.

Nothing  >>= f  =  Nothing

(Just x) >>= f  =  Just (f x)

`S`	→	`a` `T` `b` \| `c`
`T`	→	`b` `S` `S` `a` \| `S`

`S`	→	\| `L`
`L`	→	`a` `,` `L` \| `a`

Test 2 Review B

Problem R2b.1.

Problem R2b.2.

Problem R2b.3.

Problem R2b.4.

Problem R2b.5.

Problem R2b.6.

Problem R2b.7.

Problem R2b.8.

Problem R2b.9.