Am Freitag, 22. April 2005 16:40 schrieb Alexandre Weffort Thenorio:
> I am trying to get catch to work but I guess I am total newbie on this one.
>
> main :: IO()
> main = do
> removeFile "./newint.hex"
> hexFile <- catch (readFile int.hex) (\_ -> do putStrLn "Cannot find
> int.hex"
> getLine --Simply stop program so user can read error message
> return() --Quit)
since 'readFile int.hex' -- shouldn't that be 'readFile "int.hex"' ? -- is IO
String, the catch-branch must return a String, too.
> hexFile <- readFile "int.hex"
> --res of program goes here
> getLine
> return()
>
I suggest
main = do
removeFile "./newint.hex"
catch (do hexFile <- readFile "int.hex"
whatever you want to do now)
(putStrLn "doesn't exist")
I think that'll work,
Daniel
>
> But it keeps giving me error on getLine. How can I quit a program in case
> of an error giving an error message?
>
> Also I tried something like
>
> main :: IO()
> main = do
> ex <- doesFileExist "./newint.hex"
> if ex then removeFile "./newint.hex"
>
> But that won't work either. Any ideas? I'd like to catch different errors
> and quit program giving different error messages
>
> Last but not least I have the function
>
> outputLine keyno key orgFile = do
> let part1 = getLeft keyno (orgFile!!1)
> let part2 = getRight keyno (orgFile!!1)
> let total = part1 ++ (map toUpper key) ++ part2
> let checks = checksum (drop 1 total)
> let final = total ++ checks ++ "\n"
> newHexFile <- openFile "newint.hex" WriteMode
> hPutStrLn newHexFile (orgFile!!0 ++ "\n" ++ final ++ unlines (drop 2
> orgFile))
>
> I'd like to be able to check for stuff such as size of key and wheter keyno
> is only 1 or 0 and quit program with error message otherwise but again
> couldn't quite get catch to work.
>
> Any reading tips about subject would be appreciated.
>
> Best Regards
>
> NooK
>
>
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