Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!uw-beaver!rice!titan!dorai
From: dorai@titan.rice.edu (Dorai Sitaram)
Newsgroups: comp.lang.scheme
Subject: Re: Question with binding
Summary: Goof-correction
Message-ID: <3153@kalliope.rice.edu>
Date: 23 Apr 89 19:31:51 GMT
References: <19890421061138.6.VANMEULE@PERTA.SCRC.Symbolics.COM> <3140@kalliope.rice.edu>
Sender: usenet@rice.edu
Reply-To: dorai@titan.rice.edu (Dorai Sitaram)
Organization: Rice University, Houston
Lines: 26

In article <3140@kalliope.rice.edu> I wrote:
$The reason is that you can devise your own security blanket (and sleep
$tight ;-}) with the macro system that comes with any Scheme. The
$declare-constant and undeclare-constant that I referred to in my
$earlier posting are now simple macros. One method would be:
$
$(defmacro (declare-constant x)
$  `(put 'x 'constant t))
$
$(defmacro (undeclare-constant x)
$  `(put 'x 'constant nil))
$
$(defmacro (setq x v)
$  `(if (get 'x 'constant)
$       (error "hey watch out, salman rushdie is out to set constants!")
$       (set! x ,v)))

All the x's above should have commas before them. I guess the constant
shuttling between the new extend-syntax (which doesn't use the
backquote system) and the old def*macro (which does) has taken its
toll.

--dorai
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We must believe in free will. We have no choice.       --Isaac Bashevis Singer
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