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- To: navajo!JAR%AI.AI.MIT.EDU@navajo.stanford.edu
- Subject: Issue: PROCLAIM-LEXICAL
- From: email@example.com (Jon L White)
- Date: Thu, 30 Apr 87 16:11:01 PDT
- Cc: navajo!CL-Cleanup%SAIL@navajo.stanford.edu, navajo!KMP%MX.LCS.MIT.EDU@navajo.stanford.edu
- In-reply-to: Jonathan A Rees's message of Wed, 29 Apr 87 22:53:15 EDT
Re: KMP doesn't suggest ADDING a global lexical environment; the global
lexical environment is already there in the GENERAL and RESTRICTED
proposals. He merely suggests making it not be identical to the global
dynamic environment. This would make a total of 4 environments, not 3.
Since this "global lexical" environment isn't to be identical with the
"global fluid" environment, then it's a "new" environment as far as
Common Lisp is concerned; that's why I said he was "adding" something.
With respect to environments for a "free variable" reference, there are3,
not 4, possibilities. A lexically-bound variable isn't free, and hence
not, I thought, of concern to this discussion [which was opened up by your
attempt to clarify the semantics of free variables].
Have I misread anything here? Your proposals were clearly worded enough;
I only wanted to bring up an objection to the idea of having two totally
distinct global environments. I think calling it an "addition" or not
is a really minor point.
Re: . . . I see no reason
to impose this restriction, and I see Scheme compatibility as a big
reason that we SHOULD allow lambda-binding variables which have global
bindings. . . .
I think you misread this completely backwards. It WASN'T that you couldn't
lambda-bind anything that had a binding in the global environment. It WAS
that you couldn't lambda-bind anything that was explicitly declared or
proclaimed GLOBAL rather than SPECIAL (or LOCAL?).
In an implementation where the global fluid environment is the same as
the top-level environment (the standard state for virtually all deep
and shallow bound Lisps -- but not for Lisp 1.5), then a SETting
of any variable without a dynamically intervening lambda-binding would
just make a global/top-level binding. This would happen independently
of whether the variable was proclaimed GLOBAL or SPECIAL. But a variable
delcared GLOBAL would only affect the top-level binding; not any
intermediate SPECIAL lambda-bindings.
Do you see the difference here? or does this point need more explication?
-- JonL --