diff options
Diffstat (limited to 'chess-pos.el')
| -rw-r--r-- | chess-pos.el | 57 |
1 files changed, 46 insertions, 11 deletions
diff --git a/chess-pos.el b/chess-pos.el index c558531..46f61f2 100644 --- a/chess-pos.el +++ b/chess-pos.el @@ -232,21 +232,56 @@ color will do." This function does not check any rules, it only makes sure you are not trying to move a blank square." (while changes - (unless (symbolp (car changes)) + (if (symbolp (car changes)) + (setq changes nil) (let* ((from (car changes)) (to (cadr changes)) (piece (chess-pos-piece position from))) (if (= piece ? ) (error "Attempted piece move from blank square %s" from)) (chess-pos-set-piece position from ? ) - (chess-pos-set-piece position to piece))) - (setq changes (cddr changes))) - ;; once a piece is moved, en passant is no longer available - (chess-pos-set-en-passant position nil) - ;; toggle the side whose move it is - (chess-pos-set-side-to-move position - (not (chess-pos-side-to-move position))) - position) + (chess-pos-set-piece position to piece)) + (setq changes (cddr changes)))) + (let ((color (chess-pos-side-to-move position))) + + ;; once a piece is moved, en passant is no longer available + (chess-pos-set-en-passant position nil) + + ;; if a king or rook moves, no more castling; also, if a pawn + ;; jumps ahead two, mark it en-passantable + (let ((piece (downcase (car changes)))) + (cond + ((and (= piece ?k) + (equal (car changes) + (chess-rf-to-index (if color 7 0) 4))) + (chess-pos-set-can-castle position (if color ?K ?k) nil) + (chess-pos-set-can-castle position (if color ?Q ?q) nil)) + + ((and (= piece ?r) + (equal (car changes) + (chess-rf-to-index (if color 7 0) 0))) + (chess-pos-set-can-castle position (if color ?Q ?q) nil)) + + ((and (= piece ?r) + (equal (car changes) + (chess-rf-to-index (if color 7 0) 7))) + (chess-pos-set-can-castle position (if color ?K ?k) nil)) + + ((and (= piece ?p) + (> (abs (- (chess-index-rank (cadr changes)) + (chess-index-rank (car changes)))) 1)) + (chess-pos-set-en-passant position (cadr changes))))) + + ;; toggle the side whose move it is + (chess-pos-set-side-to-move position (not color)) + + ;; promote the piece if we were meant to + (let ((new-piece (cadr (assq :promote changes)))) + (if new-piece + (chess-pos-set-piece position (cadr changes) new-piece))) + + ;; return the final position + position)) (defun chess-search-position (position target piece) "Look on POSITION from TARGET for a PIECE that can move there. @@ -286,8 +321,8 @@ indices which indicate where a piece may have moved from." (and (= (chess-index-rank target) (if color 2 5)) (setq pos (chess-add-index target bias 0)) (chess-pos-piece-p position pos (if color ?p ?P)) - (and (chess-pos-en-passant position) - (= (chess-pos-en-passant position) target)) + ;; make this fail if no en-passant is possible + (= (or (chess-pos-en-passant position) 100) target) (setq candidates (list pos))) (if color (> p ?a) (< p ?a))) (let ((cands (list t))) |