[Retros] More than 100 positions leading to the foolish mate. Yefim 10/09/2004

[andrew buchanan]

>   The funny example: a foolish mate: 1.f3 e6 2.g4 Qh4#  Computer

> (WinBoard) 

> gives final position as: 

>    rnb1kbnr/pppp1ppp/4p3/8/6Pq/5P2/PPPPP2P/RNBQKBNR w KQkq - 0 3

>   with all possible castles!?

>   For all of us: No final position contains any castle rights! Local 

> Outdegree for them is 0. 


I'm afraid I disagree Yefim. Castling rights still remain part of the
final position. The fact that no castling can ever be played because
the game is over does not affect whether the rights exist.

For one thing, otherwise there is a paradoxical situation with draw by
repetition. The implication is that no draw can be claimed if some
castling right remains.

If castling is possible in the repeated position, then by your argument
when the game ends the third time round, castling rights disappear. So
the third position is *not* a repeat of the other two, so in fact the
game has *not* ended. So castling is legal, so a draw *is* claimable
again...

I distinguish:
(1) right to castle
(2) given the right: legality of castling move (i.e. is it the
castler's turn to move? does a piece or line of attack block a possible
castle?)
(3) given the right & legality: ability to play the castling move (i.e.
is the game over, through mate or dead position).

Cheers,
Andrew.