LEDIT on TOPS-20 and TNX.

[DEKLEER at PARC-MAXC2]

A partial answer to all the people asking about LEDIT.

A LEDIT for INTERLISP exists.  (It was developed at SRI by
Boyer.) If you want to see the code I can mail it to you.
However, this version is quite hairy to put it mildly.  I
could implement a much simplified (and only  slightly less
efficient) version, except for one thing: the interrupt
system.  The problem is that the interrupt system is shared
amongst the processes in ways I dont understand.  For
example, if you start a EMACS below your MACLISP and type
say ^x you will be back in MACLISP!!!  At least in TNX (and
I think it is the same in TOPS-20) all the usual ways of
munging the interrupt table lose;and you have to explicity
enable and disable  all the interrupts as you move between
EMACS and MACLISP.  This means you (MACLISP) has to know
what it wants all the interrupts to be and explicitly do
ATI's and DTI's.  This is what the TOPS-20 INTERLISP-LEDIT
system does.  I havent found a place in MACLISP to do this,
is there a way?  The problem is that it is impossible to get
the entire state of the interrupt system for a process from
from TNX (and TOPS-20, I think).

You might also look at the code for EXEC in INTERLISP, it is a piece
of LISP code.

Masinter just walked in and suggested another way to do it --
I'll send anoter msg if it works.
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