anchor.diff:    (setf (gethash :user-id *session*) nil)
     (setf *current-user* nil))
   
  +(defun log-in (user)
  +  (reset-current-user)
  +  (setf (gethash :user-id *session*) (object-id user)))
  +
   
   ;;
   ;; Error pages
  
positive.code:   (when (valid-user params)
      (if (gethash :user-id *session*)
          (reset-current-user))
      (setf (gethash :user-id *session*) (object-id (create-user params)))
      (redirect (format nil "/users/~A" (object-id (current-user)))))
    (redirect "/users/new"))
  
  
negative.code:   (if (null login-user)
        (render #P"sessions/new.html")
        (progn
          (log-in login-user)
          (redirect (format nil  "/users/~A" (gethash :user-id *session*))))))
  
  (defroute ("/logout" :method :DESTROY) ()
  