[Haskell-cafe] IO Help
mark at simplycompute.co.uk
Thu May 8 08:59:06 EDT 2008
Thank you very much for your fast response!
Ok, that is now changed, but everything else in my program is expecting
Catalogue without IO. Is there a way to change IO Catalogue into Catalogue?
Henning Thielemann wrote:
> On Thu, 8 May 2008, Mark Wallsgrove wrote:
>> Problem now is reading the data back into the program. When I read the
>> back into the program it comes as IO [Track]. This is the code I have
>> using to load the data:
>> loadData :: String -> Catalogue
>> loadData fileName = do x <- readFile fileName
>> return (read x :: Catalogue)
> type should be
> loadData :: String -> IO Catalogue
> But using plainly 'read' may not satisfy you, because the program will
> abort unrecoverably if the file has corrupt content. You may want to use
> 'reads' and check manually if parsing was successful:
> case reads x of
> [(cat, "")] -> return cat
> _ -> fail "corrupt file content"
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