[Haskell-cafe] IO () and IO [()]
dpiponi at gmail.com
Mon Mar 10 19:01:19 EDT 2008
On Mon, Mar 10, 2008 at 3:11 PM, Paulo J. Matos <pocm at soton.ac.uk> wrote:
> I would like to know if in fact there's any difference in practice
> between (), [()], i.e. if in practice the difference matters.
The type [()] is very similar to the type Integer and it's quite
different from () because you can count with it. For example:
main = do
count <- mapM print ["Hello","World"]
print $ "You printed " ++ show (length count) ++ " lines"
You can't do that with a IO (). Not that I actually recommend doing this.
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