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Re: Restoration of Session Variables
From: |
Volkan YAZICI |
Subject: |
Re: Restoration of Session Variables |
Date: |
Sat, 21 Oct 2006 00:15:00 +0300 |
User-agent: |
Mutt/1.4.2.1i |
On Oct 20 09:49, Neil Jerram wrote:
> Volkan YAZICI <address@hidden> writes:
> > I'm executing seperate procedures in the same Guile session initialized
> > by scm_init_guile(). Just after initialization, some global definitions
> > get loaded. While executing supplied procedures sequentially, I want to
> > restrict their access to some variables. Namely I want to set some
> > definitions as read-only. Is this possible?
> >
> > I tried playing with fluids and dynamic states but couldn't figure out a
> > solution. I'd be very appreciated to hear any kind of suggestion.
>
> Not sure I completely understand. Can you give an example of one of
> the globals that you want to be read-only, and of an eval that would
> try - and should fail - to change it?
I've solved my problem by using fluid-let. Yes, there's no fluid-let in
Guile, but we've define-syntax and make-fluid:
(define-syntax fluid-let
(syntax-rules ()
((fluid-let ((var1 val1)
(var2 val2)
...)
body1
body2
...)
(let ((var1 (make-fluid))
(var2 (make-fluid))
...)
(fluid-set! var1 val1)
(fluid-set! var2 val2)
...
(let ((var1 (fluid-ref var1))
(var2 (fluid-ref var2))
...)
body1
body2
...)))))
(define globally-editable #t)
(define protect-me #t)
(fluid-let ((protect-me protect-me))
(set! globally-editable #f)
(set! protect-me #f))
(display globally-editable)(newline)
#f
(display protect-me)(newline)
#t
As you can see, we protected the value of protect-me even it looks to
the fluid-let scope that it modified protect-me.
Regards.