On Wed, Mar 07, 2007 at 04:16:11AM +0000, cornmouse wrote:
I have a txt file, which contains a paragraph. I am trying to read the file, and pass the contents of the file as a string to another function called "createIndex". "createIndex" is a function to generate index of the input string.
Below is my code to read the file :
main :: IO () main = do putStr "Enter input file name.txt: " filename <- getLine content <- readFile filename createIndex content
createIndex :: String -> [ ([Int], String) ] createIndex {- contents of the function... -}
I am using Hugs compiler, when i execute, i got an error
One nitpick - Hugs isn't a compiler. It is a pure interpreter, and a relatively non-preferred one now, because it is much slower than ghci for small programs, and has relatively less development effort. (eg the development version of ghci has a prototype debugger).
Type error in generator *** Term : showString content *** Type : [Char] -> [Char] *** Does not match : IO a
IO>
I know the data type doesn't match. How do i go about this?
Use an adaptor function: main :: IO () main = do putStr "Enter input file name.txt: " filename <- getLine content <- readFile filename print $ createIndex content createIndex :: String -> [ ([Int], String) ] createIndex = undefined print is a standard library function of type: print :: Show a => a -> IO () That is, it turns any value that can be turned into text, and produces an action. Operationally, it displays the passed-in value on standard output (with a newline).