Clearing the screen and other such things.

[Bernard S. Greenberg <BSG@SCRC-STONY-BROOK.ARPA>]

    Date: Fri, 26 Jul 85 14:49 EDT
    From: Kent M Pitman <KMP@SCRC-STONY-BROOK.ARPA>

    As nearly as I can tell, Common Lisp offers no way to even clear the
    screen.
It hurts me to see various sanded-edged parallelipipeds and egg-shaped frobs
being offered for the reinvention of the wheel.

I think all the problems addressed in the referenced messages were solved
pretty adequately by any number of virtual terminal systems in the past
10 years, ITS's seeming to me to be the canonical one.

You provide primitives that are as general and powerful as possible.
Scroll region N lines, Insert entire character string, Delete n lines,
and so forth.   You provide an entry that says what capabilities are
available.  Extensibly.  Auto-CRLF at end of line and every other known
stupid feature, culled from the hundreds of person-years of experience
of Editor Implementors of the Time Sharing Era are assigned standard
names.   The support system masks some incompatibilities, like deleting
N lines by loop if there is no Delete N Lines in the terminal.
You do NOT attempt to simulate insertions and deletions, or any feature
X such that an acceptable redisplay program would choose a different
strategy in the absence of X.  I think that set is fairly well defined.

The "antsy standard" terminal protocol (e.g., the Ann Arbor Ambassador)
also makes not a bad cut at defining the canonical capabilities
generically.