Vladimir, I think you forgot to put Haskell-cafe as a recipient of this email, so first I'll repost what you wrote. On 6/15/06, Vladimir Portnykh wrote:

many thanks. i have the follwoing code:

module MyType (DataContainer(..)) where import Maybe data DataContainer = MyType { date :: [Maybe Double], weight ::[Maybe Double], height ::[Maybe Double] } deriving (Eq, Ord, Show)

myType = MyType { date = [38548,38562,38576,38590,38604,38618,38632,38646,38660,38674], weight = [], height = [] }

reportProblem = if isJust (height myType !! (length (date myType) - 1)) then 0 else 1

it failed to compiled saying "No instance for (Num (Maybe Double)) arising from the literal 38674 .

After reading your code for a while, I still don't know if I quite understand. Can you explain exactly what you are trying to do? My thought is that maybe you just want a list of objects, since you are indexing height at the same index as date. Then you just want a list of the structures that Duncan described. myObjects = [default {weight = 3.2}, default {weight = 7.9, date=38458},...] If not, hopefully somebody a little more knowledgable than I can help you. Bryan