[Haskell-beginners] function to read file and return list of contents not compiling

[Geoffrey Bays]

Haskellers:

I want to write a function that takes a class name and reads from a file
and then returns the
list of String of the file lines. I have experimented with various return
types, but GHC does not like any of them. Here is my function:

readData :: String -> IO String   -- what type here??
readData classNameP = do
    let fileName = classNameP ++ ".txt"
    contents <- readFile fileName
    lines contents

Not to complain, but this would not be difficult in any other language I
have tried, so I could use
some explanation. I suspect it has to do with understanding the IO Monad.

Many Thanks

Geoffrey
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