It seems to me that some additional primitive types would be useful, most of all a natural number type corresponding to an arbitrary- precision unsigned integer. Apparently Integer is defined in terms of something else in the GHC Prelude, what else might be needed to define it? Some of my other natural thoughts along these lines are positive reals and rationals, and nonzero integers. Rationals I have an idea that they might be similar to natural numbers and nonzero integers, though the nonzero and positive reals pose some nasty problems (try underflow). Would such machinations be useful to anyone else? Further down this line, I've gone off and toyed with Bool, and discovered GHC doesn't like it much. Is there a particular place within GHC I should look to see how the primitive Boolean type, and perhaps other types are handled? I'd also like to see where some of the magic behind the typing of various other built-in constructs happens, like list comprehensions, tuples, and derived classes. Cheers, Bill