Sara,
I want to take the input string sss of "update" to use in: writeFile "myFile.txt" sss of function "main" and get the value zzz from "main" to assign for the value return of "update". I think I need to change the way to declare two functions to get what I want, but I do not know how.
update :: String -> String update sss = zzz
main = do writeFile "myFile.txt" sss x <- callSystem "myFile.txt" y <- openFile "result.txt" ReadMode zzz <- hGetContents y return zzz
I do not quite get what you want to accomplish. Is it something like this? update :: String -> IO String update s = do writeFile "myFile.txt" sss callSystem "myFile.txt" z <- readFile "result.txt" return z Note that update produces a value of type IO String now: in Haskell 98, there is no escape from the IO monad. Chances are that the above is not what you want. Can you then please explain one more time what it is what you're after? Cheers, Stefan