Re: Clear Screen

[kst@sd.aonix.com (Keith Thompson)]

In <330FE569.29FA@bix.com> Tom Moran <tmoran@bix.com> writes:
> for i in 1 .. 50 loop
>   text_io.put_line(" ");
> end loop;
> -- would probably work on most systems.

A few points:

1. Text_IO.Put_Line(" ") puts an extraneous space character on each line.
   The simpler Text_IO.New_Line doesn't.

2. As someone else mentioned, Text_IO.New_Line takes a count parameter,
   which defaults to 1.  Thus, Text_IO.New_Line(50) is equivalent to
   the above loop.

3. This will leave the cursor at the bottom of the screen, which is
   probably not what you want.

4. It won't work in the 60-line window in which I'm composing this message.
   For a 24-line window or terminal, 50 newlines is excessive.

5. For Ada 95, you probably want to refer to Ada.Text_IO (though a
   library-level renaming called Text_IO is provided for compatibility).

If you know you're on a more or less VT100-compatible terminal or emulator
(most of them are these days), there's a particular character control
sequence that will clear the screen and home the cursor:

   <escape>[H<escape>[2J

If you're on a Unix system, you can use interface to system() and invoke
the /usr/bin/clear command, though this is likely to be slow.  Or you
can interface to the termcap, terminfo, or curses library; I don't know
of a commonly available Ada binding for any of these.

-- 
Keith Thompson (The_Other_Keith) kst@sd.aonix.com <http://www.aonix.com> <*>
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