(defconstant uncolored 'uncolored)

(defclass node ()
  ((name :accessor name :initarg :name)
   (color :accessor color :initarg :color :initform uncolored)))

(defclass graph ()
  ((nodes :accessor V :initform (make-hash-table)) ; name ->  node
   (edges :accessor E :initform (make-hash-table)) ; name -> (name)
   ))

(defun add-node (graph name)
  (let ((new-node (make-instance 'node :name name)))
    (setf (gethash name (v graph)) new-node)
    'ok
    ))

(defun get-node (graph name)
  (gethash name (v g)))

(defun get-connections (graph name)
  (gethash name (e g)))

; This works
(defun connect-nodes (graph name1 name2)
  (let ((node1 (get-node g name1)) (node2 (get-node g name2)))
    (unless (or (eq node1 'nil) (eq node2 'nil))
      (setf (gethash name1 (e g)) (adjoin name2 (get-connections g name1)))
      (setf (gethash name2 (e g)) (adjoin name1 (get-connections g name2)))
      'ok
      )))

; This fails
(defun connect-nodes-2 (graph name1 name2)
  (let ((node1 (get-node g name1)) (node2 (get-node g name2)))
    (unless (or (eq node1 'nil) (eq node2 'nil))
      (setf (get-connections g name1) (adjoin name2 (get-connections g name1)))
      (setf (get-connections g name2) (adjoin name1 (get-connections g name2)))
      'ok   ; ^ Aparently this isn't defined?
      )))