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Issue: PROCLAIM-SCOPE (Version 1)
- To: KMP@STONY-BROOK.SCRC.Symbolics.COM
- Subject: Issue: PROCLAIM-SCOPE (Version 1)
- From: Jon L White <email@example.com>
- Date: Thu, 1 Sep 88 23:06:39 PDT
- Cc: CL-Cleanup@SAIL.Stanford.EDU
- In-reply-to: Kent M Pitman's message of Wed, 31 Aug 88 19:21 EDT <880831192150.7.KMP@GRYPHON.SCRC.Symbolics.COM>
re: Proposal (PROCLAIM-SCOPE:ADD-KEYWORD-PERVASIVE):
Introduce a :LOCALLY keyword parameter to PROCLAIM which controls
the scope of a proclamation.
(PROCLAIM proclamation :LOCALLY T)
In a file, this would put the PROCLAMATION into effect for the entire
rest of time during which the file was being loaded (including
Interactively, it would be the same as :LOCALLY NIL.
(PROCLAIM proclamation :LOCALLY NIL)
In a file or interactively, this would put the PROCLAMATION into
effect permanently. (The declaration would not be retracted when the
file was done loading.)
Although you've called this a "scoping" issue, you've really made it an
"extent" issue. (See CLtL Chapter 3). The phraseology "... would put the
PROCLAMATION into effect for the entire rest of time during which the file
was being loaded ..." bears this out.
Lucid Common Lisp has a function called FILE-PROCLAIM, which has essentially
the same semantics as your proposal: It "retracts" all proclamations
made during the loading/compilation of the file. But we decided not to
recommend its use, precisely because we thought most users would confuse
the issue of dynamic extent with local scoping.
In fact, one of the issues in my "private" list of things that we at Lucid
are concerned about, but which have not had a satisfactory submissions to
the cleanup committee yet, is just the matter of a "Lexical Proclaim". In
the hardcopy sheet I handed out to many committee members, at the Palo Alto
meeting in March of this year, there should have been the paragraph:
(5) Add a lexical "pervasive" declaration special form; e.g,
(locally (pervasive-declare (special foo))
has syntax like 'declare, but acts more like proclaim; it pertains only
to the lexical scope indicated -- its action is not dynamically scoped.
In particular, it differs from 'declare' in that interior binding forms
"inherit" the declaration, rather than forming a "wall" against it.
This is the functionality that I would support, even though wrapping
a 'pervasive-declare' around a 'defun' has implementational consequences
similar to wrapping a non-null 'let' [i.e., there may be a non-null
-- JonL --