A couple of I/O questions

[haible (Bruno Haible)]

Peter Dudey asks:

>  How do I turn the string "13" into the fixnum 13?

Use READ-FROM-STRING or PARSE-INTEGER.

> Is there any way to move the cursor around the screen ... ?

CLISP contains a fairly portable mini-curses like screen access package.
Here is a documentation of it. (It mentions windows, but only one window
is possible now: the full (virtual) screen.)

99.2. Random Screen Access
--------------------------

(SYSTEM::MAKE-WINDOW)
  returns a "window stream". As long as this stream is open, the terminal
  is in cbreak/noecho mode. *TERMINAL-IO* shouldn't be used for input or
  output during this time. (Use WITH-KEYBOARD and *KEYBOARD-INPUT* instead.)

(SYSTEM::WINDOW-SIZE window-stream)
  returns the window's size, as two values:
  height (= Ymax+1) and width (= Xmax+1).

(SYSTEM::WINDOW-CURSOR-POSITION window-stream)
  returns the position of the cursor in the window, as two values:
  line (>=0, <=Ymax, 0 means top), column (>=0, <=Xmax, 0 means left margin).

(SYSTEM::SET-WINDOW-CURSOR-POSITION window-stream line column)
  sets the position of the cursor in the window.

(SYSTEM::CLEAR-WINDOW window-stream)
  clears the window's contents and puts the cursor in the upper left corner.

(SYSTEM::CLEAR-WINDOW-TO-EOT window-stream)
  clears the window's contents from the cursor position to the end of window.

(SYSTEM::CLEAR-WINDOW-TO-EOL window-stream)
  clears the window's contents from the cursor position to the end of line.

(SYSTEM::DELETE-WINDOW-LINE window-stream)
  removes the cursor's line, moves the lines below it up by one line and
  clears the window's last line.

(SYSTEM::INSERT-WINDOW-LINE window-stream)
  inserts a line at the cursor's line, moving the lines below it down by
  one line.

(SYSTEM::HIGHLIGHT-ON window-stream)
  switches highlighted output on.

(SYSTEM::HIGHLIGHT-OFF window-stream)
  switches highlighted output off.

(SYSTEM::WINDOW-CURSOR-ON window-stream)
  makes the cursor visible, a cursor block in most implementations.

(SYSTEM::WINDOW-CURSOR-OFF window-stream)
  makes the cursor invisible, in implementations where this is possible.


I suggest a macro like

(defmacro with-window (&body body)
  `(LET ((*WINDOW* (SYS::MAKE-WINDOW)))
     (UNWIND-PROTECT (PROGN ,@body) (CLOSE *WINDOW*))
   )
)

to ensure that the window stream is closed in all cases.

                    Bruno Haible
                    haible@ma2s2.mathematik.uni-karlsruhe.de