+(defun clear-patches ()
+ (setf
+ *patches*
+ (loop
+ :for y :from (max-pycor) :downto (min-pycor)
+ :append (loop
+ :for x :from (min-pxcor) :to (max-pxcor)
+ :collect (make-patch
+ :xcor (coerce x 'double-float)
+ :ycor (coerce y 'double-float)
+ :color 0d0)))))
+
+(defun clear-turtles ()
+ (setf *turtles* nil)
+ (setf *current-id* 0))
+
+(defun clear-ticks ()
+ (setf *ticks* nil))
+