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Subject: [SG10] P0074R0: Making std::owner_less more flexible
From: Nelson, Clark (clark.nelson_at_[hidden])
Date: 2016-02-23 15:14:15

We really need to update SD-6 on isocpp.org before another meeting goes by.

P0096R1 in the pre-Jacksonville mailing is lacking rationale for quite a few
C++17 features added in Lenexa and Kona, but I think we're just going to
have to live with that.

But there's also a technical issue that I think we need to consider fixing.

For P0074R0, the document currently says "none" for the macro (with
editorial question marks) but also lists a value and a header. This is
obviously incoherent.

As was pointed out at the December 16 meeting, P0074 proposes a new
application of the technique originally adopted from N3421 (Making Operator
Functors greater<>). The suggestion was made that we consider updating the
value of the associated macro: __cpp_lib_transparent_operators.

That seems like a good idea, but there's a slight issue with it: for the
C++14 feature, the macro is defined in <functional>, but the change in P0074
applies to <memory>.

So I'm tempted to suggest that an implementation that has P0074 should
define __cpp_lib_transparent_operators to be 201510 in <memory> *and also*
<functional>, whereas an implementation that has N3421 but not P0074 should
define it to be 201210 in <functional> (only).

Also, I got the section number wrong for that row; it should be 20.7,
not 20.8. So I'd like to move it up a couple of rows.

I have made the proposed changes in the attached document.

Please reply indicating whether you would like me to update SD-6 based on
the attachment, or on P0096R1 from the mailing -- or if you'd rather I not
update it at all. (I think that pretty much exhausts the available
alternatives, unless there's some other very small tweak to be made.)

Clark Nelson            Chair, PL22.16 (ANSI C++ standard committee)
Intel Corporation       Chair, SG10 (C++ SG for feature-testing)
clark.nelson_at_[hidden]  Chair, CPLEX (C SG for parallel language extensions)

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