Author: Ricardo Gibert
Date: 01:25:53 11/16/00
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On November 16, 2000 at 02:51:47, Tony Werten wrote: >On November 15, 2000 at 20:40:16, Lenard Spencer wrote: > >>This question may probably be best answered by the problemists, but if what I'm >>thinking is correct, it may be possible to make looking for double checks go a >>lot faster than the brute force approach of looking all over the board for more >>than one checker. > >The way I use it: >first, can the piece just moved attack the king (lookup table)? If so get the >direction in which it needs to travel (same lookup table) and check if there are >any other pieces blocking. > >second, can a rook or bishop attack the king from the fromsquare of the moved >piece. If so get the direction, then travel from the king in the direction of >the fromsquare until you go off the board (no discoverd check) or bump into a >piece (if piece=rook,bishop,queen then it's a discovered check) > >if ( first and second) then doublecheck:=true; > >Tony How about this position: [D]8/8/7k/6pP/8/4B3/7R/7K w - g6 The move 1.hxg6 is double check, but it is not clear to me how your algorithm catches this. >> >>Has anybody seen anything written on the subject of what makes a double check a >>"legal" double check? I mean, one that can only happen in the course of a game? >> One example, for a pawn to be involved in a double check (not counting >>promotions), it can only be on a capture, discovering a rook or queen behind it. >> >>I have been looking long and hard at this, and it seems to me (of course I'm >>only a 1250 OTB player) that there are only certain circumstances that will >>allow a legal double check. I would like to locate any material like this to >>see whether I am right or wrong. >> >>Thanks in advance for any help.
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