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Re: power set (Re: Modified keypad keys)
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From: |
Stephen Berman |
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Subject: |
Re: power set (Re: Modified keypad keys) |
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Date: |
Mon, 01 Oct 2012 11:07:26 +0200 |
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User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.2.50 (gnu/linux) |
On Mon, 1 Oct 2012 04:35:42 -0400 Christopher Monsanto <address@hidden> wrote:
> The powerset is a set of sets. The empty set is always a member of the
> powerset, as the empty set is a subset of any other set. Or in other
> words, if (length (powerset ...)) is ever zero, you have a bug. Using
> '() or nil is incorrect.
Of course you're right, and in fact I don't use nil, but (list nil) (as
the iterative version I gave entails), which is here the same as '(). I
don't know why I wrote that I use nil, brain fart I guess.
Steve Berman