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Re: lexical mumblings

From: Miles Bader
Subject: Re: lexical mumblings
Date: 20 Oct 2001 10:14:01 +0900

Richard Stallman <address@hidden> writes:
> I am not interested in changing Emacs Lisp to be lexically scoped.  It
> would be a major incompatible change.

That's the whole point of my post -- to show how it can be done
_without_ causing major incompatibilities!  I believe the change can be
done in a completely incremental way that will not break old code.

Such a change, morever, could be made in a way that it was _always_
completely optional, without having _any_ impact on code that doesn't
specify that it wants to use lexical scoping.  The changes I propose do
not make _any_ changes in the basic way the elisp execution engine
works, they simply add a few features that make it easy to support
lexical scoping.  Code that still uses dynamic scoping (which can be the
default forever if need be), will have _no_ new overhead.

> We want to make Emacs support Scheme, and one byproduct of that will
> be the availability of lexical scoping.

_That_ is a major, incompatible change, that will arguably never happen
because it will cause so much upheaval.

The changes I propose, on the other hand, are small (almost trivial),
very clean, and will have _zero_ impact on old code.  The runtime
changes could probably be implemented in a day or so.

Please keep an open mind about this Richard (and please, read my
proposal) -- lots of people want lexical scoping, and I think they can
be completely satisfied without causing any problems for those who don't

.Numeric stability is probably not all that important when you're guessing.

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