>Or.. how about a class BitSet that had proper bit operators ([]=, plus 
    >all the shifts, xors, and the like) that could be converted back and
    >forth between itself and Integer. That way, you'd have the bit class
    >for bit semantics, but which made no promises about arithmetic, but
    >which could morph into a Fixnum or Bignum as appropriate.

Sounds good to me.  If you're twidding bits, you aren't likely
to want to suddenly add 42 to the number.

/\ndy