help with code for combinations/permutations

[cpsoct at my-deja.com]

Oh, then i misunderstood. Anyway i didn't see your post on this thread.
I am reading on www.deja.com and it, while cool in some respects, seems
to break threads up often. I have a hard time seeing all the items on a
thread.  Anyway, Thanks very much for your reply to my bunching and
nesting questions.

I'll search back and see if i can find your code on this thread i only
saw the message that Tim Peters wrote about the question being ill-
stated so i was trying to re-imagine the problem from the perspective
of my own small brain.


best,

kevin parks
seoul, korea



In article <94c0np0m18 at news2.newsguy.com>,
  "Alex Martelli" <aleaxit at yahoo.com> wrote:
> <cpsoct at my-deja.com> wrote in message
news:94bbev$vai$1 at nnrp1.deja.com...
> > It is not my question, but if i may be permitted, i think i can ask
get
> > more specific. Or rather try to suggest one possibility. Do you
perhaps
> > mean something that would be like this:
> >
> > permute(list, n) -- return the nth permutation of a list.
>
> Actually, the original poster explicitly asked for *combinations*, NOT
> *permutations*:
>
> > > > I need to come up with all possible combinations of the numbers
>
> and went on to use a commutative operator ('+') on the subsets, so
> I see no reason to doubt he really wanted combinations (the difference
> being that ordering of items does not distinguish combinations, while
> it is all that distinguishes permutations!-).
>
> I answered the original question, in practice, exactly by building a
> function that returns the N-th subset (combination) of a sequence --
> easy, given the isomorphism between such subsets and binary
> numbers of len(sequence) bits!-)  Enumerating permutations is
> not quite as easy, although of course quite feasible.  But anyway,
> the little Pythonish trick around this is writing this function as the
> __getitem__ method of a class wrapped around the sequence --
> that way, client-code can just loop on all 'items' (whether they be
> combinations, permutations, whatever) with a for statement.
>
> Alex
>
>


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