Author: José de Jesús García Ruvalcaba
Date: 09:18:24 04/17/99
Go up one level in this thread
On April 17, 1999 at 12:10:14, Bruce Moreland wrote: > >On April 17, 1999 at 11:19:12, José de Jesús García Ruvalcaba wrote: > >>On April 17, 1999 at 10:47:55, Bruce Moreland wrote: >> >>> >>>On April 17, 1999 at 08:31:06, Peter Klausler wrote: >>> >>>>> The hyphen following the "KQkq" could also be a square, for instance e3, which >>>>> is the target of an en-passant capture, if one is legal. >>>> >>>>No need for a square to define en-passant opportunities; >>>>the name of the file suffices. >>> >>>I'm not describing how it should be, I'm describing the standard as it exists. >>> >>>bruce >> >> In fact, the en-passant square is indicated always when the last move was a >>pawn advancing two squares, regardless if it can actually be captured en-passant >>or not. I.e. hte requirement is not the existence of a legal en-passant capture, >>but the immediate previous advance of a pawn two squares. >>José. > >Yeah, I think that is true. It results in some strangeness when you are talking >about EPD though. > >In an EPD line, if you include a "bm" (best move) tag, the move needs to be in >standard algebraic (SAN), which involves very strict disambiguation. As an >example, if there is a knight on c3, pinned to the king on e1 by a bishop on b4, >and there is another knight on g1, in standard algebraic you say "Ne2" to move >the g1 knight to e2, rather than "Nge2", the reason being that Nce2 is illegal. > >I'm not disagreeing with this, it's better than the alternative, which would be >force the (pseudo-)disambiguating "g". This would make people to take into >account illegal moves when writing a disambiguator, and that's just painful and >bad. It should be possible to take a strictly legal move list and disambiguate >accurately based upon that, it may be that in some implementation you don't have >a pseudo-legal move list, and you shouldn't be forced to construct one. > >The problem is that the "bm" tag is done right, and yet there is no legality >checking done on the en-passant square in the FEN. > >No big deal, but the result is that you get absolutely correct EPD files that >contain data that you have to verify and discard. > >Also, by the same argument I used about not having to generate a pseudo-legal >move list in order to create SAN, you shouln't have to keep an en-passant square >in your implementation, when in fact the square is bogus. > >I don't think that my program could produce a strictly legal FEN list for a real >game, it would strip the bogus en-passant squares out. It's a drag to have to >remember illegal conditions in order to generate legal statements. > >bruce I was also describing the standard as it exists (: Until somebody comes up with something better that is universally accepted, we have to live with the current one. José.
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