[meta.logical] clarify short-circuiting property #2550

jwakely · 2018-12-03T14:42:54Z

This implements the clarification I suggested in #2548 (comment) (because if Bj is not a template then talking about "instantiation of `Bj::value" doesn't make sense) and the improvement to the inequality that Thomas suggested at #2549 (comment)

It also adds an example showing a consequence of this property.

source/utilities.tex

jensmaurer · 2019-03-15T21:14:12Z

@jwakely: Ping.

jensmaurer · 2019-05-28T07:13:37Z

@jwakely: Ping^2.

jwakely · 2019-05-31T11:10:54Z

See the screengrab at #2550 (comment) for the proposed rewrite. I haven't pushed that as a commit yet, as I'd like feedback first.

jensmaurer · 2020-09-20T19:30:42Z

Looks like this needs some decision to go with @jwakely's suggestion (or not).

jensmaurer · 2020-12-04T18:58:02Z

Editorial meeting: The rephrasing seems like a clarification, but it's normatively unclear whether "declaration" or "definition" is the right constraint here. This is not subsumed by general wording elsewhere, because this exactly delineates when instantiations happen and when they don't happen, so we need to be precise. Defer to LWG to decide.

tkoeppe · 2021-06-22T15:35:48Z

@jwakely: could you perhaps schedule an LWG-bug-Monday email slot for tihs?

The type Bj might not be a template, so it doesn't make sense to talk about instantiation. Use wording similar to that in [temp.inst] p3 which specifies when a member of a template is implicitly instantiated.

jwakely · 2022-04-20T11:04:28Z

I've pushed a rewrite that addresses @CaseyCarter's comments and removes the problematic "a definition of Bi::value is required to exist" wording that @zygoloid didn't like. Now it simply says "Instantiation of Bj ::value is required".

source/meta.tex

JohelEGP · 2022-04-20T13:22:49Z

source/meta.tex

+  template<> struct conjunction : true_type { };
+  template<> struct disjunction : false_type { };


These need indexing, too. Consider contributing towards #5111.

They're not really necessary since I added "For the specialization conjunction<>, let Bi be true_type." Maybe I should remove them again.

JohelEGP · 2022-04-20T13:23:00Z

source/meta.tex

+For the specialization \tcode{disjunction<>},
+let $\tcode{B}_{i}$ be \tcode{true_type}.


Suggested change

For the specialization \tcode{disjunction<>},

let $\tcode{B}_{i}$ be \tcode{true_type}.

Based on the addition of the explicit specialization to the synopsis, and that only the primary template is present in the itemdecl environment, I believe this is not necessary.

I agree we only need one or the other. The problem with specifying this via the synopsis is that it's easy to miss among dozens of other declarations. Specifying it here doesn't have that problem.

JohelEGP · 2022-04-20T13:23:12Z

source/meta.tex

+For the specialization \tcode{disjunction<>},
+let $\tcode{B}_{i}$ be \tcode{false_type}.


Suggested change

For the specialization \tcode{disjunction<>},

let $\tcode{B}_{i}$ be \tcode{false_type}.

Based on the addition of the explicit specialization to the synopsis, and that only the primary template is present in the itemdecl environment, I believe this is not necessary.

JohelEGP · 2022-04-20T13:29:14Z

source/meta.tex

+\begin{note}
+This allows types without a \tcode{value} static data member
+to be template arguments for \tcode{conjunction}, as long as an
+earlier argument evaluates to \tcode{false}, for example:


Why is this not an example environment after the notes?

Because the prose is clarifying the normative text, which is the purpose of a note. The statement is not specific to the example in the code, it's generally true. The example is a specific example showing it. We have lots of notes that include "for example:" like this. But I don't feel strongly about it being a note.

Co-authored-by: Johel Ernesto Guerrero Peña <johelegp@gmail.com>

jwakely mentioned this pull request Dec 3, 2018

[meta.logical] unclear wording #2548

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jwakely force-pushed the meta.logical-inequality branch 2 times, most recently from 5e4b9a2 to ee8ebb4 Compare December 3, 2018 16:09

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jensmaurer added the changes requested Changes to the wording or approach have been requested and not yet applied. label Dec 7, 2018

zygoloid force-pushed the master branch from b094703 to fb99e64 Compare March 9, 2019 01:29

jwakely self-assigned this May 28, 2019

jensmaurer removed the changes requested Changes to the wording or approach have been requested and not yet applied. label Jun 6, 2019

zygoloid added the needs rebase The pull request needs a git rebase to resolve merge conflicts. label Oct 6, 2019

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jensmaurer added lwg Issue must be reviewed by LWG. not-editorial Issue is not deemed editorial; the editorial issue is kept open for tracking. and removed decision-required A decision of the editorial group (or the Project Editor) is required. labels Dec 4, 2020

jwakely added 3 commits April 20, 2022 10:53

[meta.logical] Change j > i to more precise i < j <= N

b4bc860

[meta.logical] Replace "the instantiation of Bj::value"

7b94925

The type Bj might not be a template, so it doesn't make sense to talk about instantiation. Use wording similar to that in [temp.inst] p3 which specifies when a member of a template is implicitly instantiated.

[meta.logical] Add example of short-circuiting

263f931

jwakely force-pushed the meta.logical-inequality branch from ee8ebb4 to 263f931 Compare April 20, 2022 10:24

jwakely removed the needs rebase The pull request needs a git rebase to resolve merge conflicts. label Apr 20, 2022

jwakely marked this pull request as draft April 20, 2022 10:29

proposed rewrite

4500284

JohelEGP suggested changes Apr 20, 2022

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jwakely and others added 2 commits April 20, 2022 14:59

Remove whitespace in example

0819d35

Co-authored-by: Johel Ernesto Guerrero Peña <johelegp@gmail.com>

Fix copy&paste error in conjunction descr

603ef1a

Co-authored-by: Johel Ernesto Guerrero Peña <johelegp@gmail.com>

jwakely force-pushed the meta.logical-inequality branch from b0b0017 to 603ef1a Compare April 20, 2022 14:00

jwakely mentioned this pull request Apr 20, 2022

[mem.res.pool.overview] add proper definitions of terms #1964

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tkoeppe force-pushed the main branch from 89a9fb3 to 79eb180 Compare April 19, 2024 13:54

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[meta.logical] clarify short-circuiting property #2550

[meta.logical] clarify short-circuiting property #2550

jwakely commented Dec 3, 2018

jensmaurer commented Mar 15, 2019

jensmaurer commented May 28, 2019

jwakely commented May 31, 2019

jensmaurer commented Sep 20, 2020

jensmaurer commented Dec 4, 2020

tkoeppe commented Jun 22, 2021

jwakely commented Apr 20, 2022

JohelEGP Apr 20, 2022

jwakely Apr 20, 2022

JohelEGP Apr 20, 2022

jwakely Apr 20, 2022

JohelEGP Apr 20, 2022

JohelEGP Apr 20, 2022

jwakely Apr 20, 2022

		template<> struct conjunction : true_type { };
		template<> struct disjunction : false_type { };

		For the specialization \tcode{disjunction<>},
		let $\tcode{B}_{i}$ be \tcode{true_type}.

		For the specialization \tcode{disjunction<>},
		let $\tcode{B}_{i}$ be \tcode{false_type}.

[meta.logical] clarify short-circuiting property #2550

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