diff options
Diffstat (limited to 'chess-pos.el')
| -rw-r--r-- | chess-pos.el | 52 |
1 files changed, 29 insertions, 23 deletions
diff --git a/chess-pos.el b/chess-pos.el index fc9e162..b2d4639 100644 --- a/chess-pos.el +++ b/chess-pos.el @@ -77,8 +77,8 @@ "Routines for manipulating chess positions." :group 'chess) -(defvar chess-pos-white-always-on-move nil) -(make-variable-buffer-local 'chess-pos-white-always-on-move) +(defvar chess-pos-always-white nil) +(make-variable-buffer-local 'chess-pos-always-white) (defconst chess-starting-position [;; the eight ranks and files of the chess position @@ -334,7 +334,7 @@ trying to move a blank square." (chess-pos-set-en-passant position (cadr changes)))))) ;; toggle the side whose move it is - (unless chess-pos-white-always-on-move + (unless chess-pos-always-white (chess-pos-set-side-to-move position (not color))) ;; promote the piece if we were meant to @@ -538,30 +538,36 @@ CANDIDATES is a list of position indices which indicate the piece to be moved, and TARGET is the index of the location to be moved to. Note: All of the pieces specified by CANDIDATES must be of the same -type." +type. Also, it is the callers responsibility to ensure that the piece +can legally reach the square in question. This function merely +assures that the resulting position is valid." (let ((cand candidates) (piece (chess-pos-piece position (car candidates))) - taken-piece last-cand king-pos) + other-piece last-cand king-pos) (while cand ;; determine the resulting position - (chess-pos-set-piece position (car cand) ? ) - (setq taken-piece (chess-pos-piece position target)) - (chess-pos-set-piece position target piece) - ;; find the king (only once if the king isn't moving) - (if (or (null king-pos) - (memq piece '(?K ?k))) - (setq king-pos (chess-pos-king-index position color))) - ;; can anybody from the opposite side reach him? if so, - ;; drop the candidate - (if (catch 'in-check - (chess-search-position position king-pos (not color) t)) - (if last-cand - (setcdr last-cand (cdr cand)) - (setq candidates (cdr candidates))) - (setq last-cand cand)) - ;; return the position to its original state - (chess-pos-set-piece position target taken-piece) - (chess-pos-set-piece position (car cand) piece) + (setq other-piece (chess-pos-piece position (car cand))) + (when (if color + (> other-piece ?a) + (< other-piece ?A)) + (chess-pos-set-piece position (car cand) ? ) + (setq other-piece (chess-pos-piece position target)) + (chess-pos-set-piece position target piece) + ;; find the king (only once if the king isn't moving) + (if (or (null king-pos) + (memq piece '(?K ?k))) + (setq king-pos (chess-pos-king-index position color))) + ;; can anybody from the opposite side reach him? if so, drop + ;; the candidate + (if (catch 'in-check + (chess-search-position position king-pos (not color) t)) + (if last-cand + (setcdr last-cand (cdr cand)) + (setq candidates (cdr candidates))) + (setq last-cand cand)) + ;; return the position to its original state + (chess-pos-set-piece position target other-piece) + (chess-pos-set-piece position (car cand) piece)) ;; try the next candidate (setq cand (cdr cand))) candidates)) |