On 22-Nov-1999, c_stanto <[EMAIL PROTECTED]> wrote:
> Sorry I am being a pain, just trying to understand.
>
> the error is:
>
> Function main has the type [(Prelude.IO ())] instead of IO ().
Yes, main must return an IO action, not a list of them.
> printTable :: Foo -> [IO ()]
> printTable [] = []
> printTable (x:xs) = putStrLn x : printTable xs
>
> main :: [IO ()]
> main = do
> let tab1 = ...
> printTable tab1
If you want to convert a list of IO actions into a
single action which executes each of these in turn, then
you can use the `sequence' function:
main :: IO ()
main = do
let tab1 = ...
sequence (printTable tab1)
However, it may make more sense to do the sequencing in
the `printTable' function itself:
printTable :: Foo -> IO ()
printTable [] = return ()
printTable (x:xs) = do { putStrLn x; printTable xs; }
main :: IO ()
main = do
let tab1 = ...
printTable tab1
--
Fergus Henderson <[EMAIL PROTECTED]> | "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh> | of excellence is a lethal habit"
PGP: finger [EMAIL PROTECTED] | -- the last words of T. S. Garp.
