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Subject: Re: bug#55395: What does (1 2 3 . #2) mean?
Date: Wed, 18 May 2022 16:29:51 +0200
In-Reply-To: <jwvpmkgfd88.fsf-monnier+emacs@HIDDEN>
To: Stefan Monnier <monnier@HIDDEN>
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Content preview: 14 maj 2022 kl. 15.45 skrev Stefan Monnier
<monnier@HIDDEN>:
> I do have the impression that it used to be "correct", but I can't > remember
of a single time where I actually made use of that NNN. > > And even if you
know what it means and it works correctly, i [...]
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Cc: 55395 <at> debbugs.gnu.org, Lars Ingebrigtsen <larsi@HIDDEN>
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14 maj 2022 kl. 15.45 skrev Stefan Monnier <monnier@HIDDEN>:
> I do have the impression that it used to be "correct", but I can't
> remember of a single time where I actually made use of that NNN.
>=20
> And even if you know what it means and it works correctly, it's pretty
> hard for a normal human to correctly count the depth starting from
> the root.
It is. Counting upwards from a leaf seems slightly easier.
Perhaps these attempts to generate a meaningful circularity reference is =
a fool's errand and we should just go with #!circle! or something =
similar.
Anyway, I'm attaching a patch that tries to put some meaning back in the =
` . #N` notation: it's an index into the same list, as it used to be, I =
think, prior to the switch from Floyd to Brent. This is done by keeping =
track of the index of the tortoise at all times, which isn't very =
expensive at all.
Without the patch: (rho 4 1) =3D> (1 2 3 4 5 5 5 . #3)
With the patch: (rho 4 1) =3D> (1 2 3 4 5 5 5 . #6)
which should be a mild improvement.
It's still ambiguous:
(1 1 . #1)
could mean either
#1=3D(1 . #1#)
or
#1=3D(1 1 . #1#)
and
[(1 2 3 . #0)]
could mean either
[#1=3D(1 2 3 . #1#)]
or
#1=3D[(1 2 3 . #1#)]
but maybe it's less wrong, with room for future improvement?
--Apple-Mail=_9C60AD69-423C-4E73-823B-DAA20C4ABAB0
Content-Disposition: attachment;
filename=circular-list-print-index.diff
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diff --git a/src/print.c b/src/print.c
index da4869e8fb..823bc07406 100644
--- a/src/print.c
+++ b/src/print.c
@@ -2028,12 +2028,12 @@ named_escape (int i)
union {
struct {
Lisp_Object last; /* cons whose car was just printed */
- ptrdiff_t idx; /* index of next element */
- intmax_t maxlen; /* max length (from Vprint_length) */
+ intmax_t maxlen; /* max number of elements left to print */
/* state for Brent cycle detection */
Lisp_Object tortoise; /* slow pointer */
ptrdiff_t n; /* tortoise step countdown */
ptrdiff_t m; /* tortoise step period */
+ ptrdiff_t tortoise_idx; /* index of tortoise */
} list;
struct {
Lisp_Object obj; /* object to print after " . " */
@@ -2408,10 +2408,10 @@ print_object (Lisp_Object obj, Lisp_Object printcharfun, bool escapeflag)
.type = PE_list,
.u.list.last = obj,
.u.list.maxlen = print_length,
- .u.list.idx = 1,
.u.list.tortoise = obj,
.u.list.n = 2,
.u.list.m = 2,
+ .u.list.tortoise_idx = 0,
});
/* print the car */
obj = XCAR (obj);
@@ -2582,10 +2582,8 @@ print_object (Lisp_Object obj, Lisp_Object printcharfun, bool escapeflag)
printchar (' ', printcharfun);
- /* FIXME: We wouldn't need to keep track of idx if we
- count down maxlen instead, and maintain a separate
- tortoise index if required. */
- if (e->u.list.idx >= e->u.list.maxlen)
+ --e->u.list.maxlen;
+ if (e->u.list.maxlen <= 0)
{
print_c_string ("...)", printcharfun);
--prstack.sp;
@@ -2594,22 +2592,21 @@ print_object (Lisp_Object obj, Lisp_Object printcharfun, bool escapeflag)
}
e->u.list.last = next;
- e->u.list.idx++;
e->u.list.n--;
if (e->u.list.n == 0)
{
/* Double tortoise update period and teleport it. */
+ e->u.list.tortoise_idx += e->u.list.m;
e->u.list.m <<= 1;
e->u.list.n = e->u.list.m;
e->u.list.tortoise = next;
}
else if (BASE_EQ (next, e->u.list.tortoise))
{
- /* FIXME: This #N tail index is bug-compatible with
- previous implementations but actually nonsense;
+ /* FIXME: This #N tail index is somewhat ambiguous;
see bug#55395. */
int len = sprintf (buf, ". #%" PRIdMAX ")",
- (e->u.list.idx >> 1) - 1);
+ e->u.list.tortoise_idx);
strout (buf, len, len, printcharfun);
--prstack.sp;
--print_depth;
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From: Stefan Monnier <monnier@HIDDEN>
To: Mattias =?windows-1252?Q?Engdeg=E5rd?= <mattiase@HIDDEN>
Subject: Re: bug#55395: What does (1 2 3 . #2) mean?
Message-ID: <jwvpmkgfd88.fsf-monnier+emacs@HIDDEN>
References: <4B70C9BE-B784-4B74-A081-7A8B3F8D5136@HIDDEN>
<87ilq931ay.fsf@HIDDEN> <jwvee0xjqys.fsf-monnier+emacs@HIDDEN>
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Date: Sat, 14 May 2022 09:45:15 -0400
In-Reply-To: <715F3D50-7D11-47CF-A34B-6532F1F508D7@HIDDEN> ("Mattias
=?windows-1252?Q?Engdeg=E5rd=22's?= message of "Fri, 13 May 2022 22:01:44
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>> The main goal is to avoid inf-looping and the #NNN chosen is
>> somewhat arbitrary.
> It seems to have sort-of worked before and was broken, inadvertently and
> with the best intentions, by a later change.
>
> Additionally the #N value appears to be correct for other object types. For example,
>
> [a [b #1=[[c #1# d]]]]
>
> is printed as
>
> [a [b [[c #2 d]]]]
>
> which is consistent with the manual.
I do have the impression that it used to be "correct", but I can't
remember of a single time where I actually made use of that NNN.
And even if you know what it means and it works correctly, it's pretty
hard for a normal human to correctly count the depth starting from
the root.
I suspect if we want to "do better", printing "the beginning" of the
object to which we're looping (and saying explicitly that there's
a cycle) will be a lot more useful to the average user.
[ Or we could even print "the period" rather than "the beginning". ]
>> I'm personally more bothered by the fact that those #NNN use exactly the
>> same syntax as used with `print-circle` yet they don't have the
>> same semantics.
> The syntax isn't exactly the same (#N vs #N= and #N#) but annoyingly close.
Indeed, it's not as bad as I remembered.
> For that matter I would have preferred numbering the other way, starting at
> the bottom going up, like de Bruijn indices.
I love&hate de Bruijn indices as much as the next guy, but they're not
human-friendly (even more than the "like de Bruijn levels" we currently
use).
Stefan
bug-gnu-emacs@HIDDEN:bug#55395; Package emacs.
Full text available.Received: (at 55395) by debbugs.gnu.org; 13 May 2022 20:01:53 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Fri May 13 16:01:53 2022 Received: from localhost ([127.0.0.1]:45116 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1npbU0-0001Ey-OJ for submit <at> debbugs.gnu.org; Fri, 13 May 2022 16:01:53 -0400 Received: from mail205c50.megamailservers.eu ([91.136.10.215]:53196 helo=mail193c50.megamailservers.eu) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <mattiase@HIDDEN>) id 1npbTy-0001Bf-3l for 55395 <at> debbugs.gnu.org; Fri, 13 May 2022 16:01:51 -0400 X-Authenticated-User: mattiase@HIDDEN DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=megamailservers.eu; s=maildub; t=1652472107; bh=SIK8ZfzU00JmQULaXrktkc5EWc/gsj1VuBReHIO+9T0=; h=Subject:From:In-Reply-To:Date:Cc:References:To:From; b=Yr8wzci2nBxhwpey8ZTvWglYGyb81Eek9EZnSJW3Uv2h9PpAQ2mNHYybP1Gjq2Cb5 dVCllGUteicnIBjgGubZDT/vttdCXqDp1edLX5eZMUL+TcmQLTo1o/Q3ZDlUvC/BNC Fem9AMB5ibZuS/nU6gto8F018+jNT02NfZKN94Yc= Feedback-ID: mattiase@HIDDEN Received: from smtpclient.apple (c188-150-171-71.bredband.tele2.se [188.150.171.71]) (authenticated bits=0) by mail193c50.megamailservers.eu (8.14.9/8.13.1) with ESMTP id 24DK1jKp021497; Fri, 13 May 2022 20:01:47 +0000 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.120.0.1.13\)) Subject: Re: bug#55395: What does (1 2 3 . #2) mean? From: =?utf-8?Q?Mattias_Engdeg=C3=A5rd?= <mattiase@HIDDEN> In-Reply-To: <jwvee0xjqys.fsf-monnier+emacs@HIDDEN> Date: Fri, 13 May 2022 22:01:44 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <715F3D50-7D11-47CF-A34B-6532F1F508D7@HIDDEN> References: <4B70C9BE-B784-4B74-A081-7A8B3F8D5136@HIDDEN> <87ilq931ay.fsf@HIDDEN> <jwvee0xjqys.fsf-monnier+emacs@HIDDEN> To: Stefan Monnier <monnier@HIDDEN> X-Mailer: Apple Mail (2.3654.120.0.1.13) X-CTCH-RefID: str=0001.0A742F17.627EB92B.00CB, ss=1, re=0.000, recu=0.000, reip=0.000, cl=1, cld=1, fgs=0 X-CTCH-VOD: Unknown X-CTCH-Spam: Unknown X-CTCH-Score: 0.000 X-CTCH-Rules: X-CTCH-Flags: 0 X-CTCH-ScoreCust: 0.000 X-Origin-Country: SE X-Spam-Score: 0.3 (/) X-Debbugs-Envelope-To: 55395 Cc: 55395 <at> debbugs.gnu.org, Lars Ingebrigtsen <larsi@HIDDEN> X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -0.7 (/) 13 maj 2022 kl. 19.20 skrev Stefan Monnier <monnier@HIDDEN>: > The main goal is to avoid inf-looping and the #NNN chosen is > somewhat arbitrary. It seems to have sort-of worked before and was broken, inadvertently and = with the best intentions, by a later change. Additionally the #N value appears to be correct for other object types. = For example, [a [b #1=3D[[c #1# d]]]] is printed as [a [b [[c #2 d]]]] which is consistent with the manual. > I don't think it's worth it to try and make those #NNN more precise. I have a simple patch but it is not based on master so it will have to = wait. > I'm personally more bothered by the fact that those #NNN use exactly = the > same syntax as used with `print-circle` yet they don't have the > same semantics. The syntax isn't exactly the same (#N vs #N=3D and #N#) but annoyingly = close. For that matter I would have preferred numbering the other way, starting = at the bottom going up, like de Bruijn indices. That way the numbering = would be local and wouldn't depend on where the circular subtree occurs. = Technically that would be an easy change, and if we agree that the = numbers are unreliable right now, we might as well.
bug-gnu-emacs@HIDDEN:bug#55395; Package emacs.
Full text available.Received: (at 55395) by debbugs.gnu.org; 13 May 2022 19:54:44 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Fri May 13 15:54:44 2022 Received: from localhost ([127.0.0.1]:45112 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1npbN6-0007iV-0T for submit <at> debbugs.gnu.org; Fri, 13 May 2022 15:54:44 -0400 Received: from quimby.gnus.org ([95.216.78.240]:41256) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <larsi@HIDDEN>) id 1npbN4-0007iF-3m for 55395 <at> debbugs.gnu.org; Fri, 13 May 2022 15:54:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnus.org; s=20200322; h=Content-Type:MIME-Version:Message-ID:In-Reply-To:Date: References:Subject:Cc:To:From:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=3S5PTOedpkSDirGmAIUAjVt9cM6X6WliiYZmhZo02PE=; b=rdpE6KmXnOlWVEu/jJ6J1x3K4F RSge0iTvzkSqBKT16WaAZYb5iQM7nsTi8UgfNLJOIVXReuFnIC6ghU+0xg3O/+DpSAAhUH4DHu6K/ 9xghlQU3YevQhCmfOL1plJ3CdjObkdz5O4OgclGgzlICUFTqXlcC3jGkPAy5Xus4XTKc=; Received: from [84.212.220.105] (helo=xo) by quimby.gnus.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from <larsi@HIDDEN>) id 1npbMt-00045H-F0; Fri, 13 May 2022 21:54:33 +0200 From: Lars Ingebrigtsen <larsi@HIDDEN> To: Stefan Monnier <monnier@HIDDEN> Subject: Re: bug#55395: What does (1 2 3 . #2) mean? References: <4B70C9BE-B784-4B74-A081-7A8B3F8D5136@HIDDEN> <87ilq931ay.fsf@HIDDEN> <jwvee0xjqys.fsf-monnier+emacs@HIDDEN> X-Now-Playing: Fairport Convention's _(guitar, vocal)_: "Sweet Little Rock 'n' Roller" Date: Fri, 13 May 2022 21:54:30 +0200 In-Reply-To: <jwvee0xjqys.fsf-monnier+emacs@HIDDEN> (Stefan Monnier's message of "Fri, 13 May 2022 13:20:51 -0400") Message-ID: <87ee0xyzrd.fsf@HIDDEN> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Spam-Report: Spam detection software, running on the system "quimby.gnus.org", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see @@CONTACT_ADDRESS@@ for details. Content preview: Stefan Monnier <monnier@HIDDEN> writes: > Agreed (and agreed with Andreas as well). > The main goal is to avoid inf-looping and the #NNN chosen is > somewhat arbitrary. > > I don't think it's worth it to try and make those #NNN more precise [...] Content analysis details: (-2.9 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 55395 Cc: 55395 <at> debbugs.gnu.org, Mattias =?utf-8?Q?Engdeg=C3=A5rd?= <mattiase@HIDDEN> X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) Stefan Monnier <monnier@HIDDEN> writes: > Agreed (and agreed with Andreas as well). > The main goal is to avoid inf-looping and the #NNN chosen is > somewhat arbitrary. > > I don't think it's worth it to try and make those #NNN more precise. So it seems like everybody basically agrees on that... so if Mattias wants to implement something here to give them some semantics, he can pretty much choose whatever he wants? Or just document that there's really no semantics here without print-circle, if he prefers. -- (domestic pets only, the antidote for overdose, milk.) bloggy blog: http://lars.ingebrigtsen.no
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From: Stefan Monnier <monnier@HIDDEN>
To: Lars Ingebrigtsen <larsi@HIDDEN>
Subject: Re: bug#55395: What does (1 2 3 . #2) mean?
Message-ID: <jwvee0xjqys.fsf-monnier+emacs@HIDDEN>
References: <4B70C9BE-B784-4B74-A081-7A8B3F8D5136@HIDDEN>
<87ilq931ay.fsf@HIDDEN>
Date: Fri, 13 May 2022 13:20:51 -0400
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>> It may have made more sense before the switch of cycle-detection algorit=
hm
>> from Floyd to Brent. This can be fixed by hand-coding the list iteration
>> and explicitly remembering the index of the tortoise, but would that be
>> correct? What's the spec?
>
> I don't think I've ever considered #x to be meaningful outside of
> print-circle, but I guess if we wanted to have some semantics here, I
> think I would have expected the index of the tortoise? But...
Agreed (and agreed with Andreas as well).
The main goal is to avoid inf-looping and the #NNN chosen is
somewhat arbitrary.
I don't think it's worth it to try and make those #NNN more precise.
If the arbitrariness of the specific #NNN chosen is a problem, we could
replace it with a fixed `#=A1cycle!` or something like that (or if we
want it to be more user-readable we could print something like
#cycle:<OBJ> where OBJ is the first N layers of the rest of the cycle,
like (rho 0 2) =3D> (1 2 1 2 . #cycle:(1 2 1 ...))
I'm personally more bothered by the fact that those #NNN use exactly the
same syntax as used with `print-circle` yet they don't have the
same semantics.
Stefan
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From: Andreas Schwab <schwab@HIDDEN>
To: Mattias =?utf-8?Q?Engdeg=C3=A5rd?= <mattiase@HIDDEN>
Subject: Re: bug#55395: What does (1 2 3 . #2) mean?
References: <4B70C9BE-B784-4B74-A081-7A8B3F8D5136@HIDDEN>
X-Yow: NANCY!! Why is everything RED?!
Date: Fri, 13 May 2022 18:08:33 +0200
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On Mai 13 2022, Mattias Engdegård wrote:
> Let's define (rho LEAD LOOP) as the iota list that has a loop LOOP long after LEAD initial elements:
>
> (defun rho (lead loop)
> (let ((l (number-sequence 1 (+ lead loop))))
> (setcdr (nthcdr (+ lead loop -1) l) (nthcdr lead l))
> l))
>
> Then we have:
>
> (rho 0 1) => (1 . #0)
> (rho 0 2) => (1 2 1 2 . #2)
> (rho 0 3) => (1 2 3 1 2 . #2)
> (rho 0 4) => (1 2 3 4 1 2 3 4 1 2 . #5)
> (rho 0 5) => (1 2 3 4 5 1 2 3 4 5 1 . #5)
> (rho 1 4) => (1 2 3 4 5 2 3 4 5 2 . #5)
> (rho 4 1) => (1 2 3 4 5 5 5 . #3)
>
> and so on. The pattern is not obvious to me.
>
> It may have made more sense before the switch of cycle-detection algorithm from Floyd to Brent. This can be fixed by hand-coding the list iteration and explicitly remembering the index of the tortoise, but would that be correct? What's the spec?
I don't think there is a defined meaning behind the number, it's more an
implementation detail. If you want to have precise cycle detection you
need to enable print-circle.
--
Andreas Schwab, schwab@HIDDEN
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"And now for something completely different."
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From: Lars Ingebrigtsen <larsi@HIDDEN>
To: Mattias =?utf-8?Q?Engdeg=C3=A5rd?= <mattiase@HIDDEN>
Subject: Re: bug#55395: What does (1 2 3 . #2) mean?
References: <4B70C9BE-B784-4B74-A081-7A8B3F8D5136@HIDDEN>
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Content preview: Mattias Engdegård <mattiase@HIDDEN> writes: > It may have
made more sense before the switch of cycle-detection algorithm from Floyd
to Brent. This can be fixed by hand-coding the list iteration and explicitly
remembering the index of the tortoi [...]
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Cc: 55395 <at> debbugs.gnu.org, Stefan Monnier <monnier@HIDDEN>
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Mattias Engdeg=C3=A5rd <mattiase@HIDDEN> writes:
> It may have made more sense before the switch of cycle-detection algorith=
m from Floyd to Brent. This can be fixed by hand-coding the list iteration =
and explicitly remembering the index of the tortoise, but would that be cor=
rect? What's the spec?
I don't think I've ever considered #x to be meaningful outside of
print-circle, but I guess if we wanted to have some semantics here, I
think I would have expected the index of the tortoise? But...
> If #N means 'Nth object from the top along the path to the current object=
, starting at 0' then we should have
>
> (rho 2 3) =3D> (1 2 3 4 5 . #2)
> (list (rho 2 3)) =3D> ((1 2 3 4 5 . #3))
>
> ie, adding the print depth to the index in the list. Do you agree?
I've added Stefan to the CCs; I'm sure he has an opinion.
--=20
(domestic pets only, the antidote for overdose, milk.)
bloggy blog: http://lars.ingebrigtsen.no
bug-gnu-emacs@HIDDEN:bug#55395; Package emacs.
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Subject: What does (1 2 3 . #2) mean?
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What, exactly, does the #N print notation mean (with print-circle=3Dnil)?
Let's define (rho LEAD LOOP) as the iota list that has a loop LOOP long =
after LEAD initial elements:
(defun rho (lead loop)
(let ((l (number-sequence 1 (+ lead loop))))
(setcdr (nthcdr (+ lead loop -1) l) (nthcdr lead l))
l))
Then we have:
(rho 0 1) =3D> (1 . #0)
(rho 0 2) =3D> (1 2 1 2 . #2)
(rho 0 3) =3D> (1 2 3 1 2 . #2)
(rho 0 4) =3D> (1 2 3 4 1 2 3 4 1 2 . #5)
(rho 0 5) =3D> (1 2 3 4 5 1 2 3 4 5 1 . #5)
(rho 1 4) =3D> (1 2 3 4 5 2 3 4 5 2 . #5)
(rho 4 1) =3D> (1 2 3 4 5 5 5 . #3)
and so on. The pattern is not obvious to me.
It may have made more sense before the switch of cycle-detection =
algorithm from Floyd to Brent. This can be fixed by hand-coding the list =
iteration and explicitly remembering the index of the tortoise, but =
would that be correct? What's the spec?
If #N means 'Nth object from the top along the path to the current =
object, starting at 0' then we should have
(rho 2 3) =3D> (1 2 3 4 5 . #2)
(list (rho 2 3)) =3D> ((1 2 3 4 5 . #3))
ie, adding the print depth to the index in the list. Do you agree?
Mattias Engdegård <mattiase@HIDDEN>:bug-gnu-emacs@HIDDEN.
Full text available.bug-gnu-emacs@HIDDEN:bug#55395; Package emacs.
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