On Fri, Jun 17, 2011 at 1:04 PM, Vincent Hanquez <[email protected]> wrote:
> 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
>
Thanks everybody! This is how I solved it:
import Text.CSV
import Data.Either
import System
import Data.List
main = do
[inpFileName] <- getArgs
putStrLn ("Parsing "++inpFileName++"...")
result <- parseCSVFromFile inpFileName
let errors = lefts [result]
let csvL = rights [result]
print "CSV list"
print csvL
print "Errors"
print errors
putStrLn "All done."
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