The example below shows part of the architecture I'm using for an alife project. Q1: My implementation of "simulateBrain" seems clumsy. Is there a better way to do this? Q2: The "Animal" type includes a "brain" component. I implemented that as a simple list, but perhaps it would be better to use a monad here? I tried doing that, but I couldn't figure out the syntax. The closest I got was when I defined a "type Brain g a = (RandomGen g) => RandT g (State [Neuron]) a". But that a specifies a result type, which doesn't make sense to me for a record component. Thank you, Amy ----- SAMPLE CODE ----- {-# LANGUAGE PackageImports, RankNTypes, FlexibleContexts #-} import "mtl" Control.Monad.State import Control.Monad.Random type Neuron = Int -- The real type is more complex -- An "Alife" animal data Animal = Animal { brain :: [Neuron] -- There are other fields too, of course } deriving (Show, Read) -- | Stimulates an animal's brain, and allows it to react. stimulateBrain :: (RandomGen g) -- | The number of cycles => Int -- | The signals to apply to the sensor neurons -> [Double] -- | The animal -> RandT g (State Animal) () stimulateBrain n xs = do c <- get g <- getSplit let b' = execState (evalRandT (stimulate n xs) g) (brain c) put $ c{brain=b'} -- | Feeds some input signals into a brain, and allow it to react. stimulate :: (RandomGen g) -- | The number of cycles => Int -- | The signals to apply to the sensor neurons -> [Double] -- | The neuron states -> RandT g (State [Neuron]) () stimulate k xs = return () -- The real implementation is more complex