2019-07 LWG Motions 5, 6, and 7 #3115

zygoloid · 2019-08-02T01:57:42Z

P0645R10 Text formatting
P1361R2 Integration of chrono with text formatting
P1652R1 Printf corner cases in std::format

tomaszkam · 2019-08-02T07:19:50Z

There is major duplication of the specification between the [format.string] p10 that describes alternate form and entries in [tab:format.type.int]. In addition, these two line seem to be in-conflict with regards to appending 0 as a prefix in case if octal presentation is used ('o'). The p10 says that zero value is not prefixed, while the table does not make this exception.

Could we update the table instead, and remove the description of alternate forms in p10. Floating points types alternate form be moved to p21.

tomaszkam · 2019-08-02T07:21:37Z

The [format.string] p16 duplicates information present in the corresponding tables, as they contain none entry. In addition I that causes conflict for the priting of nan. The p22 implies that we always use nan (none is equivalent to d), while p16 says that we just ue to_chars (as if printf) and does not boil down the repersenation. Could we just refer to tables?

~~Also note in p23 does not seem to have any corresponding normative wording. The p16 list only const void*.~~ (already in FIXME)

tomaszkam · 2019-08-02T08:06:38Z

Examples formatter specialization [format.formatter.spec] p6 and after [format.context] p8 miss second template parameter. Bot should use char (their use format_context).

JohelEGP

Just a few editorial improvements.

source/utilities.tex

JohelEGP · 2019-08-02T23:07:08Z

source/utilities.tex

+\tcode{Out} models \tcode{OutputIterator<const charT\&>}, and
+\tcode{formatter<}$\tcode{T}_i$\tcode{, charT>}
+meets the \newoldconcept{Formatter} requirements
+for each $\tcode{T}_i$ in \tcode{Args}.


The formatting functions above are missing this precondition.

True, but not editorial. Please file an LWG issue.

I may have been wrong.

The non v-prefixed functions are OK since the precondition is subsumed via equivalent to semantics as specified in make_format_args and family.

For the v-prefixed ones, however, they are as a Constraints: on their call site, as specified in the constructor for basic_format_arg taking a T, which is required to construct the arguments of type format_args and family.

@JohelEGP we're fine here, right? So this can be resolved? If not, can you please file an LWG issue for it?

I'll have to file a LWG issue.

After all, there's no real issue here. You could theoretically dance around with decltype to get the types needed to make an expression equivalent to calling make_format_args and thus skip its preconditions, but that's not practical.

source/utilities.tex

source/time.tex

Editorial cleanups throughout. Converted grammar to proper grammar formatting. Removed incorrect single and double quotes that caused the wording to be meaningless for wchar_t. Converted some duplicated normative wording to notes.

than { and }".

out separate positive-integer and nonnegative-integer productions for clarity.

presupposes that they are all present to instead specify what happens when some or all are absent.

rather than leaving it dangling.

of format_context, as discussed on lib reflector.

Minor editorial cleanups throughout [format.functions] Merged specification of functions with locale parameter into existing specification rather than duplicating the descriptions.

bool and charT in their respective tables rather than requiring the reader to infer how to merge the integer table into the bool and charT tables.

Co-Authored-By: Johel Ernesto Guerrero Peña <johelegp@gmail.com>

zygoloid · 2019-08-04T03:54:21Z

There is major duplication of the specification between the [format.string] p10 that describes alternate form and entries in [tab:format.type.int]. In addition, these two line seem to be in-conflict with regards to appending 0 as a prefix in case if octal presentation is used ('o'). The p10 says that zero value is not prefixed, while the table does not make this exception.

Could we update the table instead, and remove the description of alternate forms in p10. Floating points types alternate form be moved to p21.

I would prefer we do it the opposite way around. We currently have (roughly) one paragraph per component of the std-format-spec grammar and I'd like to keep it that way.

tomaszkam · 2019-08-04T06:56:04Z

I would prefer we do it the opposite way around. We currently have (roughly) one paragraph per component of the std-format-spec grammar and I'd like to keep it that way.

I suggest leaving the paragraph, that says that # produces an alternate form, just remove the description of meaning for specifiers, so we could have in one place. The table could just say, that alternate form uses 0X prefix, instead of #.
I have also noticed other issues, the alternate form is said to be valid for any integer presentation, but there is no description information what is the alternate form for d and n.

burblebee

not done reviewing, but what I have so far...

source/utilities.tex

JohelEGP

Mostly comments on some FIXMEs.

source/utilities.tex

Fix the specification for '#' being different for octal integers in the two places it's specified.

of formatting from the format specifiers for arithmetic and string types, and make the presentation of the latter consistent with the presentation for chrono types.

creating the impression that alignment is only applied to non-string types.

described in terms of a call to to_chars.

zygoloid · 2019-08-04T22:34:12Z

Examples formatter specialization [format.formatter.spec] p6 and after [format.context] p8 miss second template parameter. Bot should use char (their use format_context).

This seems fine to me as-is; the primary template has a default argument typename charT = char.

zygoloid · 2019-08-04T22:35:21Z

There is major duplication of the specification between the [format.string] p10 that describes alternate form and entries in [tab:format.type.int]. In addition, these two line seem to be in-conflict with regards to appending 0 as a prefix in case if octal presentation is used ('o'). The p10 says that zero value is not prefixed, while the table does not make this exception.
Could we update the table instead, and remove the description of alternate forms in p10. Floating points types alternate form be moved to p21.

I would prefer we do it the opposite way around. We currently have (roughly) one paragraph per component of the std-format-spec grammar and I'd like to keep it that way.

Please take a look at the new wording; I split the difference here, defined the meaning for all cases, and (hopefully) avoided any normative duplication.

descriptions of specializations that meet those requirements.

JohelEGP

Some more editorial improvements.

source/utilities.tex

JohelEGP · 2019-08-05T03:08:46Z

source/utilities.tex

+\tcode{Out} models \tcode{OutputIterator<const charT\&>}, and
+\tcode{formatter<}$\tcode{T}_i$\tcode{, charT>}
+meets the \newoldconcept{Formatter} requirements
+for each $\tcode{T}_i$ in \tcode{Args}.


I may have been wrong.

The non v-prefixed functions are OK since the precondition is subsumed via equivalent to semantics as specified in make_format_args and family.

For the v-prefixed ones, however, they are as a Constraints: on their call site, as specified in the constructor for basic_format_arg taking a T, which is required to construct the arguments of type format_args and family.

zygoloid · 2019-08-05T03:22:56Z

Despite substantial improvements from what we were given, I'm still not very happy with this wording. Nonetheless, I think it's now good enough for the CD. If there are further comments, please open issues for them and tag them with milestone post-2019-07 so that I know to address them before finalizing the CD.

burblebee

@JohelEGP I'll open edit issues for the remaining unresolved comments. Some of those will probably need to be forwarded to LWG however.

source/utilities.tex

burblebee · 2019-08-06T00:30:23Z

@JohelEGP I'll open edit issues for the remaining unresolved comments. Some of those will probably need to be forwarded to LWG however.

It's not clear to me what issues have not been resolved here. What of the following still need to be dealt with? :

the "FIXME which one?" issue from @JohelEGP that I can no longer find in the Latex sources,
the missing preconditions on the v-prefixed formatting functions mentioned by @JohelEGP which sound like weren't an issue after all,
the two lines that "seem to be in-conflict with regards to appending 0 as a prefix in case if octal presentation is used ('o'). The p10 says that zero value is not prefixed, while the table does not make this exception" mentioned by @tomaszkam,
the duplicate information present in the corresponding tables in [format.string] p16 mentioned by @tomaszkam that "contain none entry", and
the issue from @tomaszkam where [format.string] p16 "causes conflict for the priting of nan. The p22 implies that we always use nan (none is equivalent to d), while p16 says that we just ue to_chars (as if printf) and does not boil down the repersenation. Could we just refer to tables?".

As for the FIXMEs added by @zygoloid about the wording in the Latex sources, I presume these should be filed as LWG issues? Will someone be going thru the various FIXMEs in the motions and dealing with them?

JohelEGP · 2019-08-06T03:26:23Z

Apart from the second point, those issues are resolved. As I said, I'll file an issue for the second point. Although I'm not too sure about the last one, @zygoloid removed the duplication, so the last 3 are solved. The first one was about the lack of specification about which format-spec a formatter::parse is called with. IIRC, now there are some non-normative notes about it.

zygoloid requested a review from jwakely August 2, 2019 01:57

JohelEGP suggested changes Aug 3, 2019

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zygoloid force-pushed the motions-2019-07-lwg-5-6-7 branch from 946ebb1 to 0c531d7 Compare August 4, 2019 02:49

zygoloid and others added 16 commits August 3, 2019 20:22

P0645R10 Text formatting

c42ed2a

Editorial cleanups throughout. Converted grammar to proper grammar formatting. Removed incorrect single and double quotes that caused the wording to be meaningless for wchar_t. Converted some duplicated normative wording to notes.

[format.formatter] Add subclause heading to avoid hanging paragraphs.

fb97956

[format.string] Clarify that "other characters" means "characters other

eae84a0

than { and }".

[format.string] Change 'integer' grammar to be left-recursive and factor

b62dc39

out separate positive-integer and nonnegative-integer productions for clarity.

[format.string] Fix wording that talks about omitting arg-ids but

2db4bd6

presupposes that they are all present to instead specify what happens when some or all are absent.

[format.string] Add missing grammar definition for custom-format-spec

5a32fd1

rather than leaving it dangling.

[format.string] Make tone of wording more formal and less tutorialesque.

d529b96

[format.context] Add specification of wformat_context analogous to that

3ced91d

of format_context, as discussed on lib reflector.

P1361R2 Integration of chrono with text formatting

b1008e3

Minor editorial cleanups throughout [format.functions] Merged specification of functions with locale parameter into existing specification rather than duplicating the descriptions.

P1652R1 Printf corner cases in std::format

d5300c5

[format.string] Explicitly list all the possible formatting types for

ed00761

bool and charT in their respective tables rather than requiring the reader to infer how to merge the integer table into the bool and charT tables.

[format.string] Fix whitespace collapse in format alignment example.

19d21c3

Fix collisions with the right margin.

b86e791

Add some FIXMEs for problematic wording.

5b8976a

[format.functions] Use clamp rather than min(max(a,b),c)

4662269

Co-Authored-By: Johel Ernesto Guerrero Peña <johelegp@gmail.com>

[format.arg] Don't use placeholder name for private member char-type.

a870403

zygoloid force-pushed the motions-2019-07-lwg-5-6-7 branch from 6c211d4 to a870403 Compare August 4, 2019 03:41

burblebee requested changes Aug 4, 2019

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JohelEGP reviewed Aug 4, 2019

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zygoloid added 2 commits August 4, 2019 14:04

[format.string] Avoid duplicating the specification of '#' for integers.

d17fd4d

Fix the specification for '#' being different for octal integers in the two places it's specified.

[format.string] Separate out the general (type-independent) description

e30b8a6

of formatting from the format specifiers for arithmetic and string types, and make the presentation of the latter consistent with the presentation for chrono types.

zygoloid force-pushed the motions-2019-07-lwg-5-6-7 branch from b0c43a6 to e30b8a6 Compare August 4, 2019 21:47

zygoloid added 2 commits August 4, 2019 15:09

[format.string.std] Convert normative duplication to a note to avoid

f430bec

creating the impression that alignment is only applied to non-string types.

[format.string] Further clarify description of cases where formatting is

b6454e3

described in terms of a call to to_chars.

[format.formatter] Reorder Formatter requirements before the

895f30b

descriptions of specializations that meet those requirements.

JohelEGP suggested changes Aug 5, 2019

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zygoloid merged commit c6900f9 into master Aug 5, 2019

burblebee reviewed Aug 5, 2019

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jensmaurer deleted the motions-2019-07-lwg-5-6-7 branch December 15, 2019 19:51

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2019-07 LWG Motions 5, 6, and 7 #3115

2019-07 LWG Motions 5, 6, and 7 #3115

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2019-07 LWG Motions 5, 6, and 7 #3115

2019-07 LWG Motions 5, 6, and 7 #3115

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