Re: Remove algo duplication

[Marc Glisse <marc dot glisse at inria dot fr>]

On Tue, 17 Sep 2013, Paolo Carlini wrote:
> I'm not sure however to understand in 
> detail how much of this is just helper code for the algo duplication work, 
> and how much is implementation of standard facilities. I suppose however, 
> that we should cleanly separate the C++11 code from the C++98 emulation and 
> have the latter only in predefined_ops.h or something.

In the same conversation I apparently invented, I think it was agreed that 
less<void> should be provided as an extension in C++11 (not just as a 
standard feature in C++14). This way would also provide a close enough 
emulation in C++03, but I can totally understand if you don't want one. It 
isn't specifically meant for the algo deduplication, which might use a 
completely different scheme (François has already tried several). If we 
don't do the C++03 emulation, using macros isn't worth it.

> In terms of details, we are trying not to use the deprecated unary_function / 
> binary_function, not even as implementation details. In fact if we find 
> ourselves often doing that, I don't see why we deprecated the facilities ;)

The current code for std::less uses binary_function, I didn't change it. 
It would be easy to change (a single place thanks to the macros). But in 
some sense, std::less<T> with T!=void is almost deprecated, so it isn't 
that strange that it uses a deprecated feature.

> Anyway, I seem to remember that there are concrete issues, like deprecated 
> warnings in some cases aren't completely shut up in system headers, etc. 
> Let's try to avoid those.

With macros only used in the header where they are defined, I don't think 
it is too hard for the compiler to determine that the location is in a 
system header.

--
Marc Glisse