Author: Tony Werten
Date: 23:51:47 11/15/00
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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 > >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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