-(defstruct turtle who color heading xcor ycor (label "") (label-color 9.9d0) (size 1d0) shape)
-(defstruct patch color xcor ycor)
+(defmacro with-stop-and-death-handler (&rest forms)
+ `(handler-case
+ (progn ,@forms)
+ (stop (s) (declare (ignore s)) :stop)
+ (death (d) (declare (ignore d)) :death)))
+
+(defmacro defcommand (name args docstring &rest body)
+ `(defun ,name ,args ,docstring ,@body :undefined))
+
+(defstruct turtle who breed color heading xcor ycor (label "") label-color size shape own-vars)
+(defstruct patch color xcor ycor own-vars turtles)