From: Stefan Israelsson Tampe <stefan.itampe@gmail.com>
To: Noah Lavine <noah.b.lavine@gmail.com>
Cc: guile-devel <guile-devel@gnu.org>
Subject: Re: redo-safe-variables and redo-safe-parameters
Date: Wed, 27 Mar 2013 17:15:22 +0100 [thread overview]
Message-ID: <36877746.VlrjcRTRXD@warperdoze> (raw)
In-Reply-To: <CA+U71=P6pg1ztTe0m_cwM9AyFyDUoV0PEu+CMjRyQ70gHeUJbA@mail.gmail.com>
On Wednesday, March 27, 2013 11:29:39 AM Noah Lavine wrote:
> On Wed, Mar 27, 2013 at 11:04 AM, Stefan Israelsson Tampe <
>
> stefan.itampe@gmail.com> wrote:
> > Hi Noha,
> >
> > On Wed, Mar 27, 2013 at 3:29 PM, Noah Lavine
> > <noah.b.lavine@gmail.com>>
> > wrote:
> > > Hello,
> > >
> > >
> > > On Wed, Mar 27, 2013 at 9:22 AM, Stefan Israelsson Tampe
> >
> > > <stefan.itampe@gmail.com> wrote:
> > I don't understand the difference. If I use ~, I get redo-safe
> > behavior, and
> >
> > > if I use !, I get regular behavior (value shared between dynamic
> > > states). Can I use ~ and ! on the same variable at different
> > > places in the code?>
> > If
> >
> > > yes, doesn't it have to switch behavior?
> >
> > using set! means that you basically destroys the redo safe property.
> > There is no sound concept where you mix them. If you want to mix
> > them
> > use ~ and add correct function guards to describe the semantics.
> > ...
>
> You want to allow a user to let one variable behave as with set! and
> one as
> > with
> > set~. It is not broken, the useres sees ~ on one of the varibles and
> > ! on the other.
>
> Yes, I agree. What I'm saying is, there should be two different ways
> to declare the variables, and once a variable is declared, you should
> not need to look elsewhere in the code to see whether it acts like a
> regular or redo-safe variable. If that is what you specified, I
> apologize, but I thought that it wasn't.
Hmm, your really are right in the sense that the common ideom in
computer language design is to type a variable at the declaration of
the variable. So basically a user would then do something like
(for ((~ i) from 0) code ...) to force the intruduction of a redo safe
variable. Hmm yolly good. This might be the better semantic and not
trust so much on some magic. I would still require (set~ i 1) and (~
i) for these variables? With this approach you might want to consider
to change with-redo-varibles e.g.
(with-redo-variables (((~ a) 1)) code ...)
to guard it in a redo safe manner and then
(with-redo-variables ((a 1)) code ...)
as a normal variable and beeing a noop. Error checking can be done via
macros so now everything can be made ontop on a rich syntax system and
r5rs.
Does this sounds like as a better approach?
> In particular, I think that having an MIT-Scheme-style fluid-let will
> do the right thing here. I would be interested in talking about its
> interaction with closure variables, but I think that it's the right
> thing here with regard to continuations and mutable state.
>
> > BTW. srfi's shouuld be careful about specifying dynamic state in
> > order to achieve thread safe concpets, Scheme48 is threadsafe with
> > their fluid-let, guile would not be.
>
> Yes, that's an interesting point.
I think that I will rewrite the specification with the help of
the assumption of the pressense of parameters srfi. I think that is
smart.
/Stefan
next prev parent reply other threads:[~2013-03-27 16:15 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-26 17:40 redo-safe-variables and redo-safe-parameters Stefan Israelsson Tampe
2013-03-26 18:05 ` Noah Lavine
2013-03-26 20:43 ` Stefan Israelsson Tampe
2013-03-26 21:07 ` Noah Lavine
[not found] ` <CAGua6m0WyG2_Bk3+b8UDn6ee=mddmmaOPQiF9sJf+jYtE3LsgQ@mail.gmail.com>
2013-03-26 21:38 ` Noah Lavine
2013-03-26 22:01 ` Stefan Israelsson Tampe
2013-03-26 22:36 ` Noah Lavine
2013-03-27 7:13 ` Stefan Israelsson Tampe
2013-03-27 12:42 ` Noah Lavine
2013-03-27 13:22 ` Stefan Israelsson Tampe
2013-03-27 14:29 ` Noah Lavine
2013-03-27 15:04 ` Stefan Israelsson Tampe
2013-03-27 15:29 ` Noah Lavine
2013-03-27 16:15 ` Stefan Israelsson Tampe [this message]
2013-03-27 21:44 ` Noah Lavine
2013-03-27 21:46 ` Noah Lavine
2013-03-28 8:36 ` Stefan Israelsson Tampe
2013-03-27 21:37 ` Stefan Israelsson Tampe
2013-03-28 18:03 ` Stefan Israelsson Tampe
2013-03-31 21:16 ` Stefan Israelsson Tampe
2013-04-01 1:23 ` Noah Lavine
2013-04-01 1:37 ` Daniel Hartwig
-- strict thread matches above, loose matches on Subject: below --
2013-04-01 10:17 Stefan Israelsson Tampe
2013-04-03 19:36 Stefan Israelsson Tampe
2013-04-13 10:12 ` Stefan Israelsson Tampe
2013-04-04 21:13 Stefan Israelsson Tampe
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