README file for Retractor 1.0 Retractor is a tool for retro problem composers and solvers. It allows interactive retraction of moves from any legal position, with the computer checking for common illegalities. Retractor also has a solving capability, in which it will search for the last n moves for a specified value of n. -------------------------------------------------------------------------- To setup Retractor: 1) Unzip the RETRAC10.ZIP file. Be sure you select the option to recreate the directory structure. If you are using WinZip, make sure the "Use Folder Names" box is checked. Other utilities should have a similar option. This should create a directory called c:\Retractor. This directory should have the files: RETRACTOR.EXE -- the executable RETRACTOR.HLP -- the help files RETRACTOR.CNT -- the table of contents for the help files README.TXT -- the file you are reading right now Problems -- a subdirectory containing 20 problems you can try with Retractor. 2) Double click on the icon for RETRACTOR.EXE, and you're ready to start! The first time you run Retractor, Retractor will ask you to select the notation you want for the chess pieces. There are 3 default languages you can select, or you can manually enter any letter for each piece (all letters must be distinct, of course). This notation will be used in solutions displayed by Retractor, in problem text files output by Retractor, and in Forsythe notation that you use to enter a position. ---------------------------------------------------------------------------- Getting started with Retractor: 1) Retractor starts in Setup Mode. Here, you can place pieces on the board by selecting the desired piece and color with the buttons to the right of the chessboard. To place a piece on the chessboard, left-click on the desired square. To remove a piece from the chessboard, right-click on that square. You can't add more than one king for each side, nor can you add a pawn to the first or last rank. You can also enter a position in Forsythe notation. Press Alt-P (or select "Enter Position in Forsythe Notation..." from the Board menu) and enter the position; Retractor will set up the position for you. You must enter the position using letters in the current notation. To change the notation, select "Notation" from the Board menu. 2) When you are done setting up the position, press Ctrl-M (or the "Switch Mode" button). Retractor will check the position for any illegalities. If it finds any, it will report an error message and you will need to correct the position. Note that when you leave Setup Mode, the color selected in the "Color" box will be the side to retract a move first. If one side is in check, then that color must be set to the side that is NOT in check. 3) If Retractor finds no obvious illegalities, then this places the program in Retraction mode. In this mode, you can begin retracting any legal moves. To retract a move, click on the starting, then on the ending square. To uncapture a piece, unpromote a piece, or uncapture en passant, use the buttons to the right side of the chessboard, or right-click to bring up a menu. To uncastle, just make the king move. If an illegality arises, Retractor will reject the move with an error message; otherwise, it will make the retraction. You can use Ctrl-Z to take back a retraction, or Ctrl-Y to replay a retraction. This allows you to step back and forth through the retractions that you've made. The right column of the window shows the number of pieces on each side, the number of pawn captures made by each side, and the total number of pawn captures. Note that the total number of pawn captures may be more than the sum of the pawn captures made by each side. This is because there are some capture situations in which we know that a capture was made, but not by which side. (For example: White pawn a3, Black pawn a2.) 4) To have Retractor solve a position for the last n moves, press Ctrl-L or select "Solve" from the "Retraction" menu. Enter the number of moves, set any other options you want (see Help file for details), and click on Solve. Depending on the position, Retractor may solve instantaneously or take a long time! When Retractor is done, it will report all solutions it found in a "Solutions" box. Click on the first column of a solution, and then on a move number heading, to go to that move. The easiest way to step through all the moves of a solution is to click on its first column and then click on the last move number heading. Reactive the main chessboard window, and then use Ctrl-Z and Ctrl-Y (undo and redo) to step through the moves. NOTE: IF YOU HAVE MADE ANY RETRACTIONS, THEY WILL BE LOST ON A SOLVE (you won't be able to undo them). If you want to keep the retractions, be sure to press Ctrl-S to save the position first. 5) Retractor comes with a number of retro problems, mostly of the "Last n moves?" variety. They should be in the "Problems" subdirectory. You can open these up and solve them yourself or have Retractor solve them. ------------------------------------------------------------------------------------------- Troubleshooting problems: 1) Make sure you see the entire chessboard window. At some resolutions, the window doesn't always open up all the way. Click on the maximize button to fix that. You should see a chess board, a "color" and a "piece" box, and then a column of information on piece counts, captures, move number. 2) Display problems: If the chessboard comes up with "fuzzy" color squares, or if you simply don't like the default colors, you can fix this by changing the colors of the squares. Go to the Board menu, select "Colors", and then select the item whose color you want to change. You can change the colors of the white squares, black squares, or of the highlight used when you have selected a piece to retract in Retraction mode. 3) The total number of pawn captures may be more than the sum of the pawn captures made by each side. This is because there are some capture situations in which we know that a capture was made, but not by which side. (For example: White pawn a3, Black pawn a2.) 4) Windows NT: For reasons we don't know, the solver freezes up on some problems in some machines running Windows NT. It has something to do with the launching of a separate thread for solving. We don't know of a good solution to this; if you have ideas, please contact us (see below for contact information). This has been seen to happen on the "lastmov1", "lastmov2", and "lastmov3" problems distributed with Retractor. (All of those problems should be solved instantaneously.) This is not known to happen on machines running Windows 95. ---------------------------------------------------------------------------- Contacting the authors: If you have any comments, suggestions, bug reports, etc., you can e-mail the authors at: Theodore Hwa (hwatheod@cs.stanford.edu) Chad Whipkey (whipkey@cs.stanford.edu)