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From: "daniel.kruegler at googlemail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/108760] ranges::iota is not included in <numeric>
Date: Wed, 10 Jan 2024 19:08:13 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108760

--- Comment #3 from Daniel Kr=C3=BCgler <daniel.kruegler at googlemail dot =
com> ---
(In reply to Michael Levine from comment #2)
> (In reply to Daniel Kr=C3=BCgler from comment #1)
> > (In reply to =E5=BA=B7=E6=A1=93=E7=91=8B from comment #0)
> > > It seems wrong that libstdc++ needs to include <algorithm> for ranges=
::iota.
> >=20
> > I agree, this looks like a defect, both std::iota and std::ranges:iota =
are
> > specified to be part of header <numerics>
>=20
> Should it not require including <algorithm> even though it seems to be a =
use
> of a constrained algorithm through C++20 that is in the namespace
> std::ranges?  https://en.cppreference.com/w/cpp/algorithm

Following https://cplusplus.github.io/LWG/lwg-defects.html#1178 we have
according to [res.on.headers] p1

"A C++ header shall provide the declarations and definitions that appear in=
 its
synopsis."

and I'm interpreting this that an implementation needs to make it work with=
out
requiring the user to include <algorithm>.

But we have https://cplusplus.github.io/LWG/issue3679 which raises a similar
question for a different issue. If the libstdc++ maintainers think that the
current wording does require a conforming program to include <algorithm>, I
think that an LWG issue would be required.=