Py2.3: Feedback on Sets (fwd)

Gregor Lingl glingl at aon.at
Sat Aug 16 20:58:59 CEST 2003


David Mertz schrieb:

>>* Is there a compelling need for additional set methods like
>>   Set.powerset() and Set.isdisjoint(s) or are the current
>>   offerings sufficient?
> 
> 
> I confess that I have not used sets for anything beyond testing.  I love
> the concept, but I just haven't had the need yet (especially in
> something where I want to require 2.3).
> 
> The mention of Set.powerset() above is quite interesting to me.  It
> feels both exciting and dangerous :-).

I think it would be more general and versatile to provide a method for
the Cantorproduct of two sets, set1.cantorproduct(set2), which could be
used to define Set.powerset.
Additionally implementing this as __mul__ and __pow__ methods, so you
could write set1*set2 and set**n would be funny.

Regards, Gregor

> 
> As we all know, the size of the powerset of S, for len(S)==N, is 2**N.
> Seems like it would be really easy to run into some long runtimes and
> memory usage.  Then again, power set really is a fundamental operation
> on sets.  And making users rewrite it each time is error prone.
> 
> So I think I would advocate it, but with a fairly harsh warning in the
> documentation about complexity issues.
> 
> Yours, David...
> 
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