[Retros] Retractor 2.0 now available online

Steve Dowd sdowd367 at gmail.com
Thu Apr 15 12:00:48 EDT 2021

Wasn't there for a time the designation "C" in addition to "C+" to indicate computer checked but under constraints?

Sent from my iPhone

> On Apr 15, 2021, at 9:00 AM, Elkies, Noam <elkies at math.harvard.edu> wrote:
> Bernd Gräfrath <retromode at web.de> writes:
>> Theodore writes: "if all but one solution can be eliminated by some additional
>> reasoning (like in P1012898), then the problem can be marked C+".
>> In the context of testing with Jacobi and added constraints deduced from
>> human reasoning, the mark "HC+" was suggested. See
>> https://juliasfairies.com/wp-content/uploads/Contraintes_Jacobi.pdf
>> Perhaps this is similar enough to the case described by Theodore?
>> But as the authors of the Jacobi-paper write, the mark "HC+"
>> should really be reserved for cases where the logical proof
>> is complete, without merely "plausible" hypotheses.
> But that, like Theodore's proposal, would bring us back where we started:
> an "HC+" mark by itself is no better than "H+", and human reasoning
> sometimes contain holes big enough for a cook to slip through.
> So the "H" part should be specified so we can judge it for ourselves.
> For example, "C+ assuming the last move was not Rb8xNa8";
> better yet, "C+ assuming the last move was not Rb8xNa8,
> which is impossible because . . . " followed by a proof.
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