generics with multiple constraints

Hello everyone,

suppose I want to create a generic class

  A [B -> COMPARABLE  & HASHABLE]

meaning that I want classes B that can act as a parameter to A
to descend from both COMPARABLE and HASHABLE. How can I
achieve this? Eiffel's syntax seems to allow only one constraint per
formal parameter. Is there some workaround? This looks like a fairly
standard situation to me, so maybe someone encountered this
before?

Thanks,
Felix