Tit for tat

[John Ladasky]

On Tuesday, April 28, 2015 at 1:10:14 PM UTC-7, Robert Kern wrote:
> On 2015-04-28 07:58, Steven D'Aprano wrote:

> I do believe he is trying to make a crude joke.

I agree, that's what he's doing.  And I find it ironic, since he started this thread, and seemed to invite a serious discussion of the topic.

I thought that Patrick Grim's analysis was very interesting, showing that the Spatialized Iterated Prisoner's Dilemma (SIPD) could emulate the Wireworld cellular automaton, which is a Turing-complete system.  Thus, the SIPD, a seemingly simple system at first glance, includes configurations which are formally undecidable in the Gödelian sense.  I'm not sure whether Grim proved that an SIPD which includes the Tit for Tat strategy could emulate Wireworld, but it seems likely that one could be built.