In [1]:

    

-- let see the putStrln type
:t putStrLn


    

    





putStrLn :: String -> IO ()

In [2]:

    

-- the type of getLine
:t getLine


    

    





getLine :: IO String

In [4]:

    

-- putStr come from putChar
putStr :: String -> IO ()
putStr [] = return ()
putStr (x:xs) = do
    putChar x
    putStr xs


    

In [5]:

    

-- sequence with map
sequence (map print [1, 2, 3, 4, 5])


    

    





Use mapM
Found:
sequence (map print [1, 2, 3, 4, 5])
Why Not:
mapM print [1, 2, 3, 4, 5]






    






1
2
3
4
5
[(),(),(),(),()]

In [6]:

    

-- equal above
mapM print [1,2,3]


    

    






1
2
3
[(),(),()]

In [7]:

    

mapM_ print [1,2,3]


    

    






1
2
3

In [8]:

    

import Control.Monad


    

In [9]:

    

inut <- getLine


    

    





: hGetLine: end of file

In [10]:

    

input = "hello wrold"
putStrLn input


    

    






hello wrold

In [11]:

    

return ()