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#-:classes (load "classes")
; Make the class ship and its instance variables be known
(defclass ship ((x 0) (y 0) (xv 0) (yv 0) (mass 0) (name 'unknown)
(captain 'unknown) (registry 'unknown)))
(defmethod ship :sail (time)
; the METHOD for sailing
(princ (list "sailing for " time " hours\n"))
; note that this form is expressed in terms of objects: "self"
; is bound to the object being talked to during the execution
; of its message. It can ask itself to do things.
(setf (send self :x)
(+ (send self :x) (* (send self :xv) time)))
; This form performs a parallel action to the above, but more
; efficiently, and in this instance, more clearly
(setq y (+ y (* yv time)))
; Cute message for return value. Tee Hee.
"Sailing, sailing, over the bountiful chow mein...")
; <a SHIP: #12345667> is not terribly instructive. How about a more
; informative print routine?
(defmethod ship :print () (princ (list
"SHIP NAME: " (send self :name) "\n"
"REGISTRY: " (send self :registry) "\n"
"CAPTAIN IS: " (send self :captain) "\n"
"MASS IS: " (send self :mass) " TONNES\n"
"CURRENT POSITION IS: "
(send self :x) " X BY "
(send self :y) " Y\n"
"SPEED IS: "
(send self :xv) " XV BY "
(send self :yv) " YV\n") ) )
; and an example object.
(definst ship Bounty :mass 50
:name 'Bounty
:registry 'England
:captain 'Bligh)
(send Bounty :print)
(definst ship lollipop :mass (+ 10 20) :captain 'Temple :x 1000 :y 2000)
(send lollipop :print)
(definst ship hard :mass 1000 :captain 'Bozo :registry 'North-pole )
(send hard :print)
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