Re: C++ PATCH for C++17 class template placeholders

[Marc Glisse <marc.glisse@inria.fr>]

On Wed, 5 Oct 2016, Jason Merrill wrote:

> On Wed, Oct 5, 2016 at 5:29 AM, Marek Polacek <polacek@redhat.com> wrote:
>> On Wed, Oct 05, 2016 at 08:58:08AM +0200, Marc Glisse wrote:
>>> On Tue, 4 Oct 2016, Jason Merrill wrote:
>>>
>>>> C++17 adds the ability to omit the template arguments for a class
>>>> template when declaring a variable with an initializer, much like auto
>>>> but supporting a wider variety of initialization.  This is intended to
>>>> replace functions like make_tuple.
>>>
>>> Nice. Is there a macro to test for this feature? I couldn't find it in the
>>> latest sg10 list.
>>
>> And in a similar vein, is there a macro for Selection statements with
>> initializer?  Can't find it anywhere.
>
> Not currently, for either.  The rationale for not defining macros for
> some features is that for convenience features like this, anyone
> concerned about portability will just write code the old way.

Thanks. Sadly, this ignores the case of a library that wants to provide an 
explicit deduction guide for its own types to progressive users compiling 
with a C++17 compiler, without preventing C++14 users from using the 
library the old way.

-- 
Marc Glisse