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* [Bug libstdc++/106803] New: views::adjacent_transform should not return views::empty<tuple<>> when N == 0
@ 2022-09-01 16:37 hewillk at gmail dot com
2022-09-01 16:43 ` [Bug libstdc++/106803] " hewillk at gmail dot com
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: hewillk at gmail dot com @ 2022-09-01 16:37 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106803
Bug ID: 106803
Summary: views::adjacent_transform should not return
views::empty<tuple<>> when N == 0
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: hewillk at gmail dot com
Target Milestone: ---
views::adjacent_transform seems to incorrectly copy-paste views::adjacent's
operator(), which makes it return views::empty<tuple<>> when N == 0, however,
according to the standard, it should return views::zip_transform(F) which is
views::empty<decay_t<invoke_result_t<FD&>>>.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug libstdc++/106803] views::adjacent_transform should not return views::empty<tuple<>> when N == 0
2022-09-01 16:37 [Bug libstdc++/106803] New: views::adjacent_transform should not return views::empty<tuple<>> when N == 0 hewillk at gmail dot com
@ 2022-09-01 16:43 ` hewillk at gmail dot com
2022-09-01 17:10 ` ppalka at gcc dot gnu.org
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: hewillk at gmail dot com @ 2022-09-01 16:43 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106803
--- Comment #1 from 康桓瑋 <hewillk at gmail dot com> ---
Another issue is that views::zip_transform returns
views::empty<decay_t<invoke_result_t<_Fp>>> when N == 0, which is not strictly
true, the standard requires that the return is the result of the *lvalue* F
being invoked, that is, views::empty<decay_t<invoke_result_t<decay_t<_Fp>&>>>.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug libstdc++/106803] views::adjacent_transform should not return views::empty<tuple<>> when N == 0
2022-09-01 16:37 [Bug libstdc++/106803] New: views::adjacent_transform should not return views::empty<tuple<>> when N == 0 hewillk at gmail dot com
2022-09-01 16:43 ` [Bug libstdc++/106803] " hewillk at gmail dot com
@ 2022-09-01 17:10 ` ppalka at gcc dot gnu.org
2022-09-09 19:05 ` cvs-commit at gcc dot gnu.org
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: ppalka at gcc dot gnu.org @ 2022-09-01 17:10 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106803
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |ppalka at gcc dot gnu.org
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Last reconfirmed| |2022-09-01
--- Comment #2 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Whoops, thanks.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug libstdc++/106803] views::adjacent_transform should not return views::empty<tuple<>> when N == 0
2022-09-01 16:37 [Bug libstdc++/106803] New: views::adjacent_transform should not return views::empty<tuple<>> when N == 0 hewillk at gmail dot com
2022-09-01 16:43 ` [Bug libstdc++/106803] " hewillk at gmail dot com
2022-09-01 17:10 ` ppalka at gcc dot gnu.org
@ 2022-09-09 19:05 ` cvs-commit at gcc dot gnu.org
2022-09-09 19:09 ` ppalka at gcc dot gnu.org
2022-09-10 3:39 ` hewillk at gmail dot com
4 siblings, 0 replies; 6+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2022-09-09 19:05 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106803
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:
https://gcc.gnu.org/g:8298427f6b546cabb853edd45c009cd1967b9d38
commit r13-2569-g8298427f6b546cabb853edd45c009cd1967b9d38
Author: Patrick Palka <ppalka@redhat.com>
Date: Fri Sep 9 14:59:14 2022 -0400
libstdc++: Fix return type of empty zip_/adjacent_transform [PR106803]
PR libstdc++/106803
libstdc++-v3/ChangeLog:
* include/std/ranges (views::_ZipTransform::operator()): Correct
return type in the empty case.
(views::_AdjacentTransform::operator()): Likewise.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug libstdc++/106803] views::adjacent_transform should not return views::empty<tuple<>> when N == 0
2022-09-01 16:37 [Bug libstdc++/106803] New: views::adjacent_transform should not return views::empty<tuple<>> when N == 0 hewillk at gmail dot com
` (2 preceding siblings ...)
2022-09-09 19:05 ` cvs-commit at gcc dot gnu.org
@ 2022-09-09 19:09 ` ppalka at gcc dot gnu.org
2022-09-10 3:39 ` hewillk at gmail dot com
4 siblings, 0 replies; 6+ messages in thread
From: ppalka at gcc dot gnu.org @ 2022-09-09 19:09 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106803
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |13.0
Status|NEW |RESOLVED
Assignee|unassigned at gcc dot gnu.org |ppalka at gcc dot gnu.org
Resolution|--- |FIXED
--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Fixed, thanks very much for the bug reports.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug libstdc++/106803] views::adjacent_transform should not return views::empty<tuple<>> when N == 0
2022-09-01 16:37 [Bug libstdc++/106803] New: views::adjacent_transform should not return views::empty<tuple<>> when N == 0 hewillk at gmail dot com
` (3 preceding siblings ...)
2022-09-09 19:09 ` ppalka at gcc dot gnu.org
@ 2022-09-10 3:39 ` hewillk at gmail dot com
4 siblings, 0 replies; 6+ messages in thread
From: hewillk at gmail dot com @ 2022-09-10 3:39 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106803
--- Comment #5 from 康桓瑋 <hewillk at gmail dot com> ---
(In reply to Patrick Palka from comment #4)
> Fixed, thanks very much for the bug reports.
Hey Patrick, thanks for the prompt fix.
However, I think there may be some issues with this fix, consider:
struct F {
F() = default;
F(const F&) = delete;
void operator()() = delete;
};
auto r = std::views::zip_transform(F{});
There are two problems here, the first less important one is that F is not
callable, so views::empty<...> in the function body would be a hard error; the
second one is that when empty pack, [range.zip.transform.overview] explicitly
requires that F must be copy_constructible (this should be move_constructible
because of p2494, I have submitted LWG for this), so even if F provides
operator(), we still need to reject the above.
^ permalink raw reply [flat|nested] 6+ messages in thread
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2022-09-01 16:37 [Bug libstdc++/106803] New: views::adjacent_transform should not return views::empty<tuple<>> when N == 0 hewillk at gmail dot com
2022-09-01 16:43 ` [Bug libstdc++/106803] " hewillk at gmail dot com
2022-09-01 17:10 ` ppalka at gcc dot gnu.org
2022-09-09 19:05 ` cvs-commit at gcc dot gnu.org
2022-09-09 19:09 ` ppalka at gcc dot gnu.org
2022-09-10 3:39 ` hewillk at gmail dot com
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