On 06/17/2011 10:00 AM, Dmitri O.Kondratiev wrote:
Hi,
I try to parse csv file with Text.CSV, like this:
import Text.CSV
import System
main = do
[inpFileName] <- getArgs
putStrLn ("Parsing "++inpFileName++"...")
let result = parseCSVFromFile inpFileName
print result
=== As a result I get:
No instance for (Show
(IO (Either Text.Parsec.Error.ParseError CSV)))
arising from a use of `print'
Possible fix:
add an instance declaration for
(Show (IO (Either Text.Parsec.Error.ParseError CSV)))
=== Question:
How to add a Show instance for "(IO (Either Text.Parsec.Error.ParseError
CSV)))" ?
Hi Dmitri,
you don't add a show instance for IO, but you "unwrap" the IO Monad first and
then show the result.
let result = parseCSVFromFile inpFileName
should be:
result <- parseCSVFromFile inpFileName
--
Vincent
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