Hey everybody I've been playing around with Parsec a little bit lately. I like it a lot, but now I've hit a bit of a challenge. Suppose I have to parse a variable length string representing a time interval. Depending on how many fields there are, the time is either interpreted as seconds, minutes and seconds or hours, minutes and seconds. For example: "... 31 ..." would be parsed as 31 seconds. "... 05:31 ..." would be parsed as 5 minutes and 31 seconds. "... 01:05:31 ..." would be parsed as 1 hour, 5 minutes and 31 seconds. I've come up with the following solution using optionMaybe to deal with the problem: data ElapsedTime = ElapsedTime { hours :: Int, minutes :: Int, seconds :: Int } deriving (Show, Eq, Ord) p_elapsed_time :: CharParser () ElapsedTime p_elapsed_time = toElapsedTime <$> (optionMaybe p_Int) <*> (optionMaybe (char ':' *> p_Int)) <*> (optionMaybe (char ':' *> p_Int <* skipSpaces)) where toElapsedTime Nothing Nothing Nothing = ElapsedTime 0 0 0 toElapsedTime (Just s) Nothing Nothing = ElapsedTime 0 0 s toElapsedTime (Just m) (Just s) Nothing = ElapsedTime 0 m s toElapsedTime (Just h) (Just m) (Just s) = ElapsedTime h m s Where p_Int simply parses a sequence of digits as an Int and skipSpaces does just that. This works correctly, but it also feels kinda clumsy. For one the compiler rightly complains about non-exhaustive pattern matches in the definition of the toElapsedTime function, although I believe that's negligible in that particular case. Is there a better i.e. more elegant way to tackle such a problem? regards, david