Hi How do I include polymorphic function type signatures in a data element ? Exmaple: <CODE> type Fitness = Integer data Population a = Population [(Fitness, a)] deriving (Show) data GAParams = GAParams { randomNums :: [Integer] , someFunc :: (Int->Int->(Population a))} </CODE> This errors with parse input error on '}'. However something like this works fine: <CODE> data GAParams = GAParams { randomNums :: [Integer] , someFunc :: (Int->Int->GAParams) } /<CODE> I am just having issues with polymorphic types. Any ideas ? The context is included below in case it helps: <CODE> import Random type Fitness = Integer data Population a = Population [(Fitness, a)] deriving (Show) data GAParams = GAParams { randomNums :: [Integer] , someFunc :: (Int->Int->GAParams) } gaSolutionSpaceFrom :: Population a -> GAParams -> [Population a] gaSolutionSpaceFrom p gaParams = (evolvePopulation p gaParams) : gaSolutionSpaceFrom p newGAParams where (r,rs) = splitAt (length pl) (randomNums gaParams) Population pl = p newGAParams = (gaParams{randomNums=rs}) evolvePopulation :: Population a -> GAParams -> Population a evolvePopulation p gaParams = (mutate (cross (select p))) selectMatingPoolByRouletteWheel :: Population a -> GAParams -> Population a selectMatingPoolByRouletteWheel (Population popList) gaParams = (Population [ (rwSelect rw rnd) | rnd <- rndNums ]) where rw = createRW (Population popList) rndNums = (randomNums gaParams) rwSelect :: [(Fitness, a)] -> Fitness -> (Fitness, a) rwSelect [] _ = error "rwSelect random number outside roullete wheel range or list empty" rwSelect ((x,a):xs) z = if x <= z then rwSelect xs z else (x,a) createRW :: Population a -> [(Fitness, a)] createRW (Population xs) = (scanl1 f xs) where f (n,a) (m,b) = (n + m, a) select p = p cross p = p mutate p = p _________________________________________________________________ MSN 8 with e-mail virus protection service: 2 months FREE* http://join.msn.com/?page=features/virus