From: Stefan Israelsson Tampe <stefan.itampe@gmail.com>
To: mandyke@gmail.com, guile-devel@gnu.org
Subject: Re: redo-safe-variables and redo-safe-parameters
Date: Mon, 01 Apr 2013 12:17:16 +0200 [thread overview]
Message-ID: <1519320.kv9yxKJiCU@warperdoze> (raw)
> Daniel Writed
> Dynamic states are not suitable for the purpose. They have nothing to
> do with compenstating for the inability of continuations to backtrack
> _through side-effects_. I believe this will be obvious if you
> consider the problem of side-effects generally, rather than focusing
> only on variable assignment.
Yes, I try now to avoid dynamic states. I was a bit ignorant of the
subject. But after some reading and thought your point has become
clear to me.
> Backtracking is typically handled (at least, in part) by the
> evaluator, by either:
> - explicitly tracking side-effects, so that they can be reverted in a
> sensible manner; or
> - state-copying, that is, non-mutable environments.
Yea I have thise two features on my mind when trying to design a spec.
> I do not see how you can hope to marry the concepts of continuations
> and backtracking side-effects without modifying the evaluator, at
> which point you have continuations and an evaluation environment that
> is not Scheme, although perhaps very Scheme-like.
Note that there is a guard that checks if you should restore
or not. If that executes always to #f then everything is scheme, so it
is an extension. Actually I'm not sure if I need to change the
evaluater to get redo-safe-variables I beleve that you can get the
features by simply modify call/cc with current scheme. But for
redo-safe-parameters I do not know if the same holds. Also the latter
part of the spec handling set! and set~, AS Noha stated in his last
mail. We might just drop that part and have a recomendation for macro
writers to follow a certain pattern instead.
> It seems your real objective is to extend Scheme-embedded logic DSLs
> by supporting continuations and non-functional Scheme code within
> them. I appreciate that you have some experience in the area, can you
> point to any papers that discuss anything similar to what you are
> trying to achieve? (Not the Scheme modifications, but the logic DSL +
> side-effects + continuations).
I'm afraid that I have not seen any papers on this. But I'm
not in academia and have not a great overview of the subject. Maybe I
should write a paper about guile-log, maybe I should try to dig up a
references. Maybe I should documnet guile-log at a very detailed level.
> Back to the Scheme modifications. Perhaps I do not understand that
> problem space as well as you, but when I look at this I see a
> premature attempt to solve a problem that is _hard_. There is also no
> precedent for continuations that backtrack side-effects in any Scheme
> or Lisp I know of, and noone will miss that if you do not acheive it.
> Clearly you are spending some effort on this, and I do not like to see
> anyone wasting efforts. IMO this specific path is unproductive.
Yea that path is unproductive, right now I pursue other paths.
To be onest, I do this mainly to learn. But also because I find it
interesting and useful. The hard part actually seams not to implement
something that are redo safe. The hard part is to do it in a way so
that you will get easy to reason about code and possible efficient
imlementations. Much of the confusion is attributed to this.
/Stefan
next reply other threads:[~2013-04-01 10:17 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-01 10:17 Stefan Israelsson Tampe [this message]
-- strict thread matches above, loose matches on Subject: below --
2013-04-04 21:13 redo-safe-variables and redo-safe-parameters Stefan Israelsson Tampe
2013-04-03 19:36 Stefan Israelsson Tampe
2013-04-13 10:12 ` Stefan Israelsson Tampe
2013-03-26 17:40 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
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
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