;;;; Corrected version of parse-where(), originally from AIMA example code,

;;;; in the file agents/environments/grid-env.lisp.

(defun parse-where (env where whats)
  (cond
   ((eq where 'EDGE)    (let ((x-size (xy-x (grid-environment-size env)))
			      (y-size (xy-y (grid-environment-size env))))
			  (for i = 0 to (- x-size 1) do
			       (parse-whats env (@ i 0) whats)
			       (parse-whats env (@ i (- y-size 1)) whats))
			  (for i = 1 to (- y-size 2) do
			       (parse-whats env (@ 0 i) whats)
			       (parse-whats env (@ (- x-size 1) i) whats))))
   ((eq where 'ALL)     (dotimes (x (xy-x (grid-environment-size env)))
			  (dotimes (y (xy-y (grid-environment-size env)))
			    (when (free-loc? (@ x y) env)
			      (parse-whats env (@ x y) whats)))))
   ((eq where 'FREE?)   (parse-whats env (random-loc env :if 'free-loc?) whats))
   ((eq where 'START)   (parse-whats env (grid-environment-start env) whats))
   ((xy-p where)        (parse-whats env where whats))
   ((eq (op where) 'AND)(for each w in (args where) do 
			     (parse-where env w whats)))
   (t (warn "Unrecognized object spec ignored: ~A" `(at ,where ,@whats)))))