box.lisp

(defclass box ()
  ((location :accessor location :initarg :location :initform (vector 0 0))
   (dimensions :accessor dimensions :initarg :dimensions :initform (vector 1 1))))

(defmethod x ((b box))
  (aref (location b) 0))

(defmethod y ((b box))
  (aref (location b) 1))

(defmethod (setf x) (new-val (b box))
  (setf (aref (location b) 0) new-value))

(defmethod (setf y) (new-val (b box))
  (setf (aref (location b) 1) new-value))

(defmethod width ((b box))
  (aref (dimensions b) 0))

(defmethod height ((b box))
  (aref (dimensions b) 1))

(defmethod (setf width) (new-val (b box))
  (setf (aref (dimensions b) 0)
        new-val))

(defmethod (setf height) (new-val (b box))
  (setf (aref (dimensions b) 1)
        new-val))

(defmethod (setf half-width) (new-val (b box))
  (setf (width b) (* new-val 2.0)))

(defmethod (setf half-height) (new-val (b box))
  (setf (height b) (* new-val 2.0)))

(defmethod half-width ((b box))
  (* (width b) .5))

(defmethod half-height ((b box))
  (* (height b) .5))

;;; Edge Positions
;; SETFing an edge does not change dimension, rather it repositions the box
(defmethod left ((b box))
  (- (x b)
     (half-width b)))

(defmethod (setf left) (new-val (b box))
  (setf (x b)
        (+ (half-width b) new-val)))