Problem with some Elisp to start NuPRL5

[Paulo Jorge de Oliveira Cantante de Matos <pocm@netvisao.pt>]

Hi all,

Some instruction and elisp code comes with NuPRL5 to start the program.
http://www.cs.cornell.edu/Info/Projects/NuPrl/html/NuprlSystem.html

The issue is that the code is not running correctly in the latest emacs
version I have.

The code is as follows:
-------------------------------------------------
(defun nuprl5 ()
  (interactive)
  (message "Starting NuPRL 5 Library, Editor, and Refiner ...")
  (nulib)
  (sleep-for 5)
  (nuedit)
  (nurefine)
)

(defun nuprl-frame (bufname height top-corner cmd)
  (save-excursion
    (set-buffer (make-comint bufname "/bin/csh" nil "-v"))
    (switch-to-buffer-other-frame (concat "*" bufname "*"))
    (let ((NuPRLframe (car (cadr (current-frame-configuration)))))
      (set-frame-size NuPRLframe 81 height)
      (set-frame-position NuPRLframe 515 top-corner)
      )
    (set-default-font "6x10")
    (while (= (buffer-size) 0) (sleep-for 1))
    (comint-send-string bufname "limit coredumpsize 0\n")
    (comint-send-string bufname cmd)
    ) )

(defun nulib ()
  (interactive)
  (nuprl-frame "NuLibrary" 10 76 "/home/pmatos/nuprl/bin/nulib\n")
  (message "Starting Library ...")
  (set-foreground-color "Red")
  (set-background-color "#ddddff")
  (comint-send-string "NuLibrary" "(top)\n")
  (comint-send-string "NuLibrary" "go.\n")
)

(defun nurefine ()
  (interactive)
  (nuprl-frame "NuRefine" 10 280 "/home/pmatos/nuprl/bin/nuref\n")
  (message "Starting Refiner ...")
  (set-foreground-color "Green4")
  (set-background-color "#ffffbb")
  (comint-send-string "NuRefine" "(top)\n")
  (comint-send-string "NuRefine" "go.\n")
  )

(defun nuedit ()
  (interactive)
  (nuprl-frame "NuEditor" 10 178 "/home/pmatos/nuprl/bin/nuedd\n")
  (message "Starting Editor ... please be patient")
  (set-foreground-color "midnightblue")
  (set-background-color "#ffd8ff")
  (comint-send-string "NuEditor" "(top)\n")
  (comint-send-string "NuEditor" "go.\n")
  (comint-send-string "NuEditor" "win.\n")
)

(defun nuxit ()
  (interactive)
  (message "Shutting Down NuPRL 5 Library, Editor, and Refiner ...")
  (comint-send-string "NuEditor" "stop.\n")
  (comint-send-string "NuRefiner" "stop.\n")
  (sleep-for 5)
  )
------------------------------

when I do M-x nuprl5 I get:
save-excursion: Wrong type argument: stringp, nil

I really don't know what's going on. I read 
http://www-2.cs.cmu.edu/cgi-bin/info2www?(elisp)Excursions

however, I can't understand what's wrong with the code, can somebody
please help?

Cheers,
-- 

Paulo J. Matos : pocm [_at_] mega . ist . utl . pt
Instituto Superior Tecnico - Lisbon
Computer and Software Eng. - A.I.
 - > http://mega.ist.utl.pt/~pocm
---
        -> God had a deadline...
                So, he wrote it all in Lisp!