-- gaSolutionSpace :: [a] -> [a]

...

gaSolutionSpace x = x : gaSolutionSpace (evolvepopulation x)

-Stop deceiving yourself until it's too late. -Why did you comment out the type annotation? *Sheepish Grin* its historical, my original thought and attempt was that you would recieve a list of populations and evolve it to a bigger list of populations. Hence the [a] -> [a]. It didnt work out too well as this is what I came up with: gaSolSpace [x:xs] = gaSolutionSpace [x : evolePopulation x] Eventually i realised that I needed to evolve a single population, not a list, which let to a -> [a] and thanks to Keith I now have this: gaSolutionSpaceFrom :: a -> [a] gaSolutionSpaceFrom = iterate evolvePopulation Thanks _________________________________________________________________ Add photos to your e-mail with MSN 8. Get 2 months FREE*. http://join.msn.com/?page=features/featuredemail