[Retros] Retractor 2.0 now available online

Elkies, Noam elkies at math.harvard.edu
Thu Apr 15 09:59:59 EDT 2021

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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