From: Vaughan Pratt <pratt@cs.stanford.edu>
To: categories@mta.ca
Subject: Re: Addendum
Date: Sun, 16 Jan 2000 22:37:40 -0800 [thread overview]
Message-ID: <200001170637.WAA03764@coraki.Stanford.EDU> (raw)
In-Reply-To: Your message of "Sat, 15 Jan 2000 13:07:11 EST." <200001151807.NAA10666@saul.cis.upenn.edu>
> * | A B
> --+------
> A | B A
> B | A A
>
>The unique cubical coalgebra is A but there is no square coalgebra.
>
>What I don't have is a counterexample with an _associative_ bifunctor.
How about the positive integers with * as sum, with 1->3 as the only
nonidentity arrow? The unique cubical coalgebra is 1 but there is no
square coalgebra.
Vaughan
next prev parent reply other threads:[~2000-01-17 6:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-01-15 18:07 Addendum Peter Freyd
2000-01-17 6:37 ` Vaughan Pratt [this message]
2000-01-17 21:18 ` Addendum Vaughan Pratt
2000-01-18 19:47 ` Addendum Vaughan Pratt
2000-01-18 9:49 ` Addendum Dr. P.T. Johnstone
2004-03-26 13:39 Addendum Peter Freyd
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