Chess Trace

Chess Trace

This is a library that I created to display traces of famous backtracking algorithms. I have included gif-eight-queens and gif-knights-tour as examples.

http://www.jeremyenglish.org/packs/chess-trace.tgz

Functions

"make-chess-board" will create a new chess board. You can pass a custom set of chess pieces to it and you can modify the number of rows and columns. The chess board is always square.

"start-frame" will add a new working frame to the animation.

"end-frame" will close the current frame and add it to the animation.

"add-frame-delay" will let you add a custom delay to any frame.

"output-board" writes the animation to a gif file.

"blocks" returns the number of blocks in a row or column.

"put-piece-xy" puts a chess piece on the chess board. You can pass it the name of the piece, x and y positions and the piece's color. The names are keywords and can be either :king, :queen, :pawn, :rook, :knight, :bishop, :cross or :dot. The names :cross and :dot name the extra symbols used to mark off a block. For an NxN chess board (0,0) will be the top left block and (n,n) will be on the bottom right.

Usage

You will need to have skippy and xpm-to-gif to use the library. Once you have those packages, put a link to chess-trace.asd somewhere; asdf can find it.

(asdf:oos 'asdf:load-op 'chess-trace)

This command will load the project.

(use-package :chess-trace)

(defun move-rooks ()
  (let ((cb (make-chess-board :blocks 5)))
    (dotimes (n (blocks cb))
      (start-frame cb)
      (when (> n 0)
             (dotimes (m n)
               (put-piece-xy cb :name :dot :x 0 :y m)
               (put-piece-xy cb :name :dot :x m :y 0)))
        (put-piece-xy cb :name :rook :x 0 :y n :color :black)
        (put-piece-xy cb :name :rook :x n :y 0 :color :black)
        (end-frame cb :delay-time 20))
      (add-frame-delay 300 cb))
      (output-board cb #p"rooks.gif")))

(move-rooks)

This function will create a 5 by 5 chess board with a rook moving toward white and another one moving along the back row. It will look like this:

See gif-knights-tour.lisp and gif-eight-queens.lisp for some more examples.

Author: Jeremy English <jhe@jeremyenglish.org>

Date: 2007/06/28 08:11:11 PM