anchor.diff:          (reset-current-user))
       (log-in (create-user params))
       (flash "Welcome to the Sample App!")
  -    (redirect (format nil "/users/~A" (current-user-id))))
  +    (redirect-back-or (format nil "/users/~A" (current-user-id))))
     (redirect "/users/new"))
   
   (defroute "/users/:id" (&key id)
  
positive.code:                              (get-value-from-params "password" params))
        (log-in login-user)
        (flash "Welcome to the Sample App!")
        (redirect (format nil  "/users/~A" (gethash :user-id *session*)))))
    (flash "Invalid email/password combination")
    (render-with-current #P"sessions/new.html"
                         (list :flash (flash)
  
negative.code:   (gethash :user-id *session* nil))
  
  (defun reset-current-user ()
    (remhash :user-id *session*)
    (remhash :forwarding-url *session*))
  
  (defun log-in (user)
    (reset-current-user)
  