From: Harry Ohlsen <harryo@...>
Date: 2001-05-27T11:10:05+09:00
Subject: [ruby-talk:15783] Re: Subsets of a set

Harry Ohlsen wrote:

> I know that the Array class has a number of methods that make it usable
> for storing sets.
>
> What I need is a method that will allow me to generate all of the
> subsets of a given set
> that are a certain size.

By the way, I'd be happy to accept a routine which returns the set of ALL
subsets
(ie, the power set), because I could easily code something to extract
elements of
a given size from that.

At least, that would be fine for sets of a reasonable size, since
I actually want to
generate them all, just grouped into sets of the various possible sizes.

For any mathematicians out there, what I'm working on is something to
generate
all of the discrete topologies for a given set.  Someone here recently did
it in C++, but
their code runs for a very long time and I'd like to see if I can write
something neater
in Ruby.

Also, I want to extend it to the generation of Hasse diagrams for the
topologies.