[boost] Re: powerset

From: David B. Held (dheld_at_[hidden])
Date: 2002-08-28 19:49:18

"Dave Gomboc" <dave_at_[hidden]> wrote in message
news:Pine.LNX.4.44.0208281646430.21018-100000_at_boyne.cs.ualberta.ca...
> [...]
> I'm sure the originator of the proposed name (not myself) didn't pick
> the term out of left field.  Would you not agree that the union of all of
> the possible values that can be assigned to the structure (whatever
> its name) is the power set of the individual items represented by the
> bits?
> [...]

No, I would not agree, though I may be totally off-base for doing so.
I would expect a "power set" to include all the subsets of a set, and
offer some way to access them.  I don't see the proposed library as
offering this capability.  To take a simple example:

Set S:
{0, 1, 2}

Power set P(S):
{{}, {0}, {1}, {2}, {0, 1}, {0, 2}, {1, 2}, {0, 1, 2}}

Now, while the set library in question can represent *each* of the
elements of the power set, as you say, I don't see it as *being* the
power set.  I suppose I would expect an actual "power set library"
to perhaps offer, say, iterators for all the 0-th order elements, all
the 1st order elements, etc.  I think "domain" is more mathematically
accurate, though perhaps not as obvious to programmers as is
desired.  There should be a way to characterize the various set types
being proposed and in existence, and probably name them
according to the major discriminating features.

Dave