diff options
| -rw-r--r-- | chess-pos.el | 38 |
1 files changed, 36 insertions, 2 deletions
diff --git a/chess-pos.el b/chess-pos.el index d92fdf7..edf0a13 100644 --- a/chess-pos.el +++ b/chess-pos.el @@ -265,8 +265,8 @@ return the position of the black king." (assert (vectorp position)) (assert (memq color '(nil t))) (or (aref position (if color 72 73)) - (aset position (if color 72 73) - (chess-pos-search position (if color ?K ?k))))) + (chess-pos-set-king-index position color + (chess-pos-search position (if color ?K ?k))))) (defsubst chess-pos-set-king-index (position color index) "Set the known index of the king on POSITION for COLOR, to INDEX. @@ -552,6 +552,40 @@ This string should have been created by `chess-pos-to-string'." chess-pos-piece-values))))) value)) +(defun chess-pos-passed-pawns (position color &optional pawn-indices) + "If COLOR has Passed Pawns in POSITION, return a list of their indices. +Optionally, if INDICES is non-nil those indices are considered as candidates. + +A Pawn whose advance to the eighth rank is not blocked by an +opposing Pawn in the same file and who does not have to pass one +on an adjoining file is called a passed Pawn." + (let ((seventh (if color 1 6)) (bias (if color -1 1)) (pawn (if color ?p ?P)) + pawns) + (dolist (index (or pawn-indices + (chess-pos-search position (if color ?P ?p))) pawns) + (if (= (chess-index-rank index) seventh) + (push index pawns) + (let ((file (chess-index-file index))) + (if (catch 'passed-pawn + (let ((test (chess-incr-index index (if color -1 1) 0))) + (while (funcall (if color '>= '<=) + (chess-index-rank test) seventh) + (if (if (and (> file 0) (< file 7)) + (or (chess-pos-piece-p position test pawn) + (chess-pos-piece-p + position (chess-incr-index test 0 1) pawn) + (chess-pos-piece-p + position (chess-incr-index test 0 -1) pawn)) + (or (chess-pos-piece-p position test pawn) + (chess-pos-piece-p + position + (chess-incr-index test 0 (if (zerop file) 1 -1)) + pawn))) + (throw 'passed-pawn nil) + (setq test (chess-incr-index test (if color -1 1) 0)))) + t)) + (push index pawns))))))) + (chess-message-catalog 'english '((move-from-blank . "Attempted piece move from blank square %s"))) |