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Subject: Re: Question about Gerbil

Author: Dann Corbit

Date: 15:55:45 07/11/01

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On July 11, 2001 at 18:42:19, Heiner Marxen wrote:
[snip]
>I have not yet looked into the sources of Gerbil, please excuse my ignorance.
>
>If the above means "can actually be taken by a *legal* move", then it appears
>to be really new.

I'm not positive which is the case.  I only read through the section once, and
so I am not positive which it is.  In any case, it's a really good idea.

>If thew above means "can actually be taken by a *pseudo legal* move",
>then this is not really new.  It has been discussed some time ago (on this
>board IIRC).  E.g. Chest does so, by setting the flag "e.p. is possible"
>within move execution only for those pawn double steps with an enemy pawn
>in the correct position (left or right of the moving pawn's target).
>This is not perfect, but much better than flagging each double step.
>
>As a consequence the FEN generated from such positions is not strictly
>correct according to the standard from SJE, but IMO the standard should
>be changed, here.

Yes, I think the current PGN standard is broken in regard to e.p. squares.

For instance, how many distinct positions is this:
[D]rnbqkbnr/ppp1pppp/8/3p4/3P4/8/PPP1PPPP/RNBQKBNR w KQkq -
You can make 4 of them, if you have to set e.p. flags, but there is only one
real position.  Multiply the number of potential pawns affected and it explodes
with great stupidity.




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