From: Alan Baker swarthmore edu> Date: 29 aug 2004 Subject: shogi promotion rule -- logical flaw? Your free subscription is supported by today's sponsor: ------------------------------------------------------------------- Save up to 80% on Inkjet & Toner Supplies. 100% Satisfaction=20 Guarantee. Free Shipping on orders over $49. www.inksoutlet.com http://click.topica.com/= caacAsfa2i6YsbnuqMaa/Inksoutlet ------------------------------------------------------------------- As the recent exchange on this list has shown, it is not easy to correctly = state the conditions under which a piece must be promoted. Pieter Stouten's original statement of the condition was as follows: "A piece must be promoted when, upon completion of its move, it has no lega= l move left." Larry Kaufman correctly points out that this is too weak (for example it wo= uld include cases where the square in front happened to be occupied by a 'frien= dly' piece). Larry's proposed amendment is: "A piece must promote only when it arrives at a square from which it could = never have a legal move." I take Larry's stronger condition to mean "could never have a legal move at= any possible future point in the game." However I think that this condition is still too weak. It is possible to construct positions in which a pawn moves from the 7th rank to the 8th rank= and it can be shown that there is no way that it could ever legally move again,= no matter how the game proceeds. Such positions are completely artificial and non-game-like, but they are legal. (The basic idea is to construct a line o= f pawns on the 8th rank, with pieces of the same side trapped on the 9th rank= by these pawns and preventing their promotion.) If this is right, then the condition will have to be strengthened to "A piece must promote only when it arrives at a square from which it could = never have a legal move in any game." -- Alan Baker Department of Philosophy Swarthmore College Swarthmore PA 19081 Your free subscription is supported by today's sponsor: ------------------------------------------------------------------- Sponsor a child today through Children International.=20=20 Give a desperately poor child hope for a brighter future. For only $18 a month you can make a difference! http://click.topica.com/= caacvgoa2i6YsbnuqMaf/ChildrenInternational ------------------------------------------------------------------- --^---------------------------------------------------------------- This email was sent to: = shogi-l shogi net EASY UNSUBSCRIBE click here: http://topica.com/u/?a2i6Ys.= bnuqMa.= c2hvZ2kt Or send an email to: shogi-unsubscribe topica com For Topica's complete suite of email marketing solutions visit: http://www.topica.com/?p=3DTEXFOOTER --^----------------------------------------------------------------