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From: jpayne@flam.Eng.Sun.COM (Drummer Boy)
Newsgroups: comp.emacs
Subject: emacs's extensions language
Message-ID: <1355@exodus.Eng.Sun.COM>
Date: 12 Oct 90 22:10:32 GMT
Sender: news@exodus.Eng.Sun.COM
Lines: 30


Hi there, would some nice person be willing to explain to me the
model for LISP execution inside GNU emacs?  What do I mean?  Well,
is the editor always running inside a lisp context?  Or is the
main loop written in C, and does it sit there reading the
keyboard, looking up the keys in the various keymaps, and checking
on the type of the thing it's trying to execute?  And when that
thing is a piece of LISP code, it just fires up an interpreter to
execute it?

What happens if there is an error while executing a piece of LISP
code?  If the editor is running LISP the whole time, there must be
some main loop that sits there reading and dispatching keystrokes,
right?  So when there's an error, is an error-handler fired up
which read and dispatches more keystrokes, but also lets you look
around at the state of the world?

Does emacs have multiple LISP threads at any given time?  Is there
a way to arrange to have a piece of LISP code executed when output
appears from a process?  Does EMACS stop what it's doing and fire
up that piece of LISP code, and if that piece of code sits there
in an endless loop, is EMACS hung until some sort of timeout
occurs?

I'm just trying to get a feel for how this whole thing is put
together.  I never thought about it carefully before now.

Thanks for any info.

Jonathan Payne