Sukit Tretriluxana:
I was looking around Stroustrup's website and found a simple program... I wondered how a Haskell program equivalent to it looks like...
main = E.catch (interact reverseDouble) (\_ -> print "format error") toDoubles = map (read::String->Double)
For a "safe" program in Haskell, we would not normally use an unsafe function like "read", and then try to rescue it by catching IO exceptions. Instead, we would write the program safely to begin with. Something like this (building on Jonathan's idea): import Data.Maybe (listToMaybe) main = interact reverseDouble reverseDouble = unlines . intro . maybe ["format error"] (map show . reverse) . mapM (readMaybe :: String -> Maybe Double) . takeWhile (/= "end") . words where intro l = ("read " ++ show (length l) ++ " elements") : "elements in reversed order" : l readMaybe :: Read a => String -> Maybe a readMaybe = listToMaybe . map fst . reads The function "readMaybe" returns the pure value "Nothing" if there is a format error instead of throwing an IO exception. It has been proposed to make it part of the standard libraries - I'm not sure what the status is of that process. Regards, Yitz