Ang.: Will guile support R7RS terminating "equal?" in the presence of cycle?

Ang.: Will guile support R7RS terminating "equal?" in the presence of cycle?

[stefan.itampe]

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Hi

1 I don't think the current equal? Will need to change, but
Another one that under rnr7 will be coded and used with the
Symbol equal? In that module. Hence no problems.

2 The guile hackers are able enough to implement it. In typed-guile there is an implementation that does unification on circular lists and
Also there is probably enough reference information to code this in due time.

Cheers!
Stefan

Skickat från min HTC

----- Reply message -----
Från: ludo@gnu.org (Ludovic Courtès
Till: <guile-devel@gnu.org>
Rubrik: Will guile support R7RS terminating "equal?" in the presence of cycle?
Datum: lör, sep 1, 2012 15:30


Hi,

"David A. Wheeler" <dwheeler@dwheeler.com> skribis:

> *However*, the current R7RS draft for "equal?" requires termination
> even in the presence of cycles, as well as impose other requirements
> on "write" and "display" in the presence of cycles.  Will guile
> support such changes?  I worry that these new requirements on "equal?"
> will have such a high overhead that people won't do it.  But perhaps
> those fear are misplaced.

Are you talking about termination in the case of circular lists, or for
arbitrary data structures?

The former is easy and reasonably cheap, but the latter may require more
work, indeed.

Thanks,
Ludo’.



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Re: Ang.: Will guile support R7RS terminating "equal?" in the presence of cycle?

[Ludovic Courtès]

Hi Stefan!

"stefan.itampe@gmail.com" <stefan.itampe@gmail.com> skribis:

> 1 I don't think the current equal? Will need to change, but
> Another one that under rnr7 will be coded and used with the
> Symbol equal? In that module. Hence no problems.

Yes, of course.

> 2 The guile hackers are able enough to implement it. In typed-guile there is an implementation that does unification on circular lists and
> Also there is probably enough reference information to code this in due time.

Typed Guile?  Did I miss something?  :-)

Ludo’.

Re: Ang.: Will guile support R7RS terminating "equal?" in the presence of cycle?

[Stefan Israelsson Tampe]

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> Typed Guile?  Did I miss something?  :-)
https://gitorious.org/typed-guile

It's a type system implemented using guile-log!

By the way, I do not think the overhead is that dramatic. I guess that
guile's equal would be any slower with this feature added. you typically
does a circularity check via a hare/turtouse pair and when circularity is
found one adress the issue in some way, what might be needed now is to
hook into this code and make sure that rnr7 logic is implemented for that
one version.

/Stefan

On Sat, Sep 1, 2012 at 7:26 PM, Ludovic Courtès <ludo@gnu.org> wrote:

> Hi Stefan!
>
> "stefan.itampe@gmail.com" <stefan.itampe@gmail.com> skribis:
>
> > 1 I don't think the current equal? Will need to change, but
> > Another one that under rnr7 will be coded and used with the
> > Symbol equal? In that module. Hence no problems.
>
> Yes, of course.
>
> > 2 The guile hackers are able enough to implement it. In typed-guile
> there is an implementation that does unification on circular lists and
> > Also there is probably enough reference information to code this in due
> time.
>
> Typed Guile?  Did I miss something?  :-)
>
> Ludo’.
>

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Re: Ang.: Will guile support R7RS terminating "equal?" in the presence of cycle?

[Ludovic Courtès]

Stefan Israelsson Tampe <stefan.itampe@gmail.com> skribis:

> https://gitorious.org/typed-guile
>
> It's a type system implemented using guile-log!

Woow, this is crazy.  I wish we could converge eventually...

Ludo’.

Re: Ang.: Will guile support R7RS terminating "equal?" in the presence of cycle?

[Ian Price]

ludo@gnu.org (Ludovic Courtès) writes:

> Hi Stefan!
>
> "stefan.itampe@gmail.com" <stefan.itampe@gmail.com> skribis:
>
>> 1 I don't think the current equal? Will need to change, but
>> Another one that under rnr7 will be coded and used with the
>> Symbol equal? In that module. Hence no problems.
>
> Yes, of course.

IIRC, equal? in r6rs is supposed to terminate also. If someone
implements it, please backport it to the (rnrs base) module.

-- 
Ian Price -- shift-reset.com

"Programming is like pinball. The reward for doing it well is
the opportunity to do it again" - from "The Wizardy Compiled"