;;;======================================================================
;;; Here is some info I have on vt200 escape sequences. I think they all
;;; work on vt100's also.
;;;======================================================================
;;;
;;; Operation		Command
;;; ================+================
;;; Clear Screen        ESC[2JESC[H
;;; Up N lines          ESC[NA       ; N is a variable
;;; Down N lines        ESC[NB       ; N is a variable
;;; Right N cols        ESC[NC       ; N is a variable
;;; Left N cols		ESC[ND       ; N is a variable
;;; Move cursor to
;;;   line L, col C     ESC[L;CH     ; L, C are variables
;;;
;;; If anyone wants more details (bold, reverse video, underlining, graphics
;;; chars for drawing lines and corners, etc), send me mail and I'll bring my 
;;; OLD vt220 "Pocket Guide" from which I got this info. You can probably glean
;;; it from /etc/termcap for other terminal types.
;;;
;;; Note that #\Escape is the character for ESC in Lisp; you
;;; can use (setf (aref <String> <Position>) #\Escape) to stick it in, or
;;; use (format nil ...) to construct the string. See two examples below,
;;; one doing it each way.
;;; 1995 Marty Hall. marty_hall@jhuapl.edu
;;;======================================================================

;;;======================================================================
;;; Defines a Clear-Screen function for vt100 terminals.
;;; Note that this does not work if running Lisp within emacs, only
;;; from a tty in vtxxx mode. You could put a real escape character in
;;; the file instead of sticking it in the string at run-time, but that
;;; would make it hard to view and print the source code.

(defun Clear-Screen ()
  "Clear the screen on a vt100 terminal. Don't use from within emacs."
  (let ((String " [2J [H"))
    (setf (aref String 0) #\Escape)   ; Stick ESCAPE in for the spaces
    (setf (aref String 4) #\Escape)
    (princ String)                    ; PRINC doesn't do a CR (PRINT does)
    (values) ))
    
;;;======================================================================
;;; Again, don't use this from within emacs.

(defun Move-Up (Lines)
  "On a vt100 terminal, move cursor up the specified number of lines"
  (let ((String (format nil "~A[~DA" #\Escape Lines)))  ; ie "ESC[3A"
    (format t String)
    (values)))                                          ; Suppress output

;;;======================================================================