Re: how to convert IO String to string---- still have questions

[Lu Mudong]

Thanks a lot for you guys' help.

I am very new to haskell and tried some methods you guys advised, doesn't seem to work, i think i didn't do it properly, here's my code and result, hope you can point out what's wrong. thanks!

my code:

myReadFile :: IO String
myReadFile = readFile "d:/hugs98/input.txt"

theString :: String
theString = do
s <- myReadFile
putStrLn s


the error message i got in hugs98

ERROR "D:\hugs98\parser.hs":16 - Type error in explicitly typed binding
*** Term : theString
*** Type : IO ()
*** Does not match : String

From: Ashley Yakeley <[EMAIL PROTECTED]>
To: "Ahn Ki-yung" <[EMAIL PROTECTED]>,"Haskell List" <[EMAIL PROTECTED]>
Subject: Re: how to convert IO String to string
Date: Fri, 22 Nov 2002 15:09:34 -0800

At 2002-11-22 14:49, Ahn Ki-yung wrote:

>'do' is a syntactic sugar of monadic operations.
>The original form can be written as
>
>main = myReadFile >>= \s -> putStrLn s

That's correct. In this case, the 's' has type String. So the IO String
has been 'converted' into a String, but only within the context of the IO
monad.

I think ultimately everything is syntactic sugar.

--
Ashley Yakeley, Seattle WA

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