; pitch class - represents the playing field.  it has 3 properties north  
;  and south represent the 2 opposite scoring zones and points is a list  
;  of all valid points within the playing field  
  
( defclass pitch()  
  (   
   ( nhoops :accessor pitch-nhoops :initarg :nhoops :initform '() )  
   ( shoops :accessor pitch-shoops :initarg :shoops :initform '() )  
   ( points :accessor pitch-points :initarg :points :initform '() )  
   ( midfld :accessor pitch-midfld :initarg :midfld :initform '() )  
   ( ngzone :accessor pitch-ngzone :initarg :ngzone :initform '() )  
   ( sgzone :accessor pitch-sgzone :initarg :sgzone :initform '() )  
  )  
)  
  
; hoop class - the hoop used to score points, each scoring zone contains  
;  3 hoops.  
  
( defclass hoop()   
  (   
   ( location :accessor hoop-location :initarg :location )   
  )  
)