Thinking about this some more, I ran into something else to chew on. It would seem to make a certain amount of sense to have instance (Bits b) => Bits (Seq b) with .&., .|., and xor defined using a zero-prepending zipWith variant. but there are a few challenges relating to size. Specifically: 1. The specification indicates that finiteBitSize and bitSizeMaybe are supposed to return a result based only on the type of their argument. Clearly, that will not work for this. 2. There is no obviously correct size to use for zeroBits and bit. One approach, of course, is to define something wonky like newtype SeqN (n::Nat) a = SeqN (Seq a) and then use instance (Bits b) => Bits (SeqN n b) but that gives a different, more limited type than one might expect.