how to convert IO String to string

[Ahn Ki-yung]

Ashley Yakeley wrote:

>At 2002-11-22 08:12, Lu Mudong wrote:
>  
>
>>what i need is a string,
>>    
>>
>
>You can do the conversion with "<-", but only inside a "do" block. For 
>instance:
>
>  myReadFile :: IO String
>  myReadFile = ...
>
>  main = do
>    s <- myReadFile
>    putStrLn s
>
>Here, s has type String.
>  
>

'do' is a syntactic sugar of monadic operations.
The original form can be written as

main = myReadFile >>= \s -> putStrLn s

and more short by eta-conversion

main = myReadFile >>= putStrLn