Hi Levi,
so that I can muck around with a Vector type that includes its length encoded in its type.
I suppose you have some operations over these vectors, such as nil :: Vec Zero a (|>) :: a -> Vec n a -> Vec (Succ n) a If so, you could write a SmallCheck Series instance as follows. instance Serial (Vec Zero a) where series = cons0 nil instance (Serial a, Serial (Vec n a)) => Serial (Vec (Succ n) a) where series = cons2 (|>) Let's assume the earlier ops are defined as data Vec n a = V [a] nil :: Vec Zero a nil = V [] (|>) :: a -> Vec n a -> Vec (Succ n) a x |> V xs = V (x:xs) If we have the property prop_vector :: Vec (Succ (Succ Zero)) Bool -> Bool prop_vector (V xs) = xs == xs we can check it, and only 2 element vectors will be tested: *Main> smallCheck 4 prop_vector Depth 0: Completed 0 test(s) without failure. Depth 1: Completed 0 test(s) without failure. Depth 2: Completed 4 test(s) without failure. Depth 3: Completed 4 test(s) without failure. Depth 4: Completed 4 test(s) without failure. Now, it seems what you really want to do is define polymorphic properties like prop_poly :: Vec n Bool -> Vec n Bool -> Bool and have SmallCheck check all equal-sized vectors. If so, good question! :-) Anybody else? Matt.