[Retros] How many times could a Diagram be repeated during aproofgame?

Rol, Guus G.A.Rol at umcutrecht.nl
Tue Feb 10 03:25:15 EST 2009

I just sent 2 problems to "Probleemblad" regarding castling rights in
Circe and AP-logic as well. They show amongst others that even "the same
castling right" is not always "the same"! These examples are particular
to AP-logic; I doubt it makes sense in general to distinguish "an
original Circe castling right" from "a restored Circe castling right".
Compare it to two knights switching position. The knight identities may
be different but their combined impact on the board position is the

For those interested here one of the Circe-problems:

Stipulation: H#2.5 Circe (AP), 2 solutions (use Circe retro-analysis)
White: Kb5, Qa2, Pa4,Pb2,Pc4,Pd5
Black: Ke8, R:a8, Pc5.

Guus Rol.

>In some fairy types, e.g. Circe, castling rights CAN be restored. Two

externally identical positions may appear one after another on the

>chessboard, differing in that e.g. white has lost the castling right in

the first position and has regained it in the second.

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