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Subject: Re: Question about Gerbil

Author: Dann Corbit

Date: 16:12:47 07/11/01

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On July 11, 2001 at 19:02:24, Bruce Moreland wrote:

>On July 11, 2001 at 18:55:45, Dann Corbit wrote:
>
>>>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.
>
>Wait a sec.  Does the FEN standard according to SJE state that you *have* to
>have the ep square set to e3 after 1. e4?  If so, that is dumb and I'm going to
>happily ignore it.  The square shouldn't be set unless there is a legal capture,
>or at least it should be optional to set it if there isn't.

"16.1.3.4: En passant target square

The fourth field is the en passant target square.  If there is no en passant
target square then the single character symbol "-" appears.  If there is an en
passant target square then is represented by a lowercase file character
immediately followed by a rank digit.  Obviously, the rank digit will be "3"
following a white pawn double advance (Black is the active color) or else be
the digit "6" after a black pawn double advance (White being the active color).

An en passant target square is given if and only if the last move was a pawn
advance of two squares.  Therefore, an en passant target square field may have
a square name even if there is no pawn of the opposing side that may
immediately execute the en passant capture."

Notice the second paragraph.
Ugh.



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