The future of concepts

The future of concepts

[Piotr Wyderski]

Concepts have recently been removed from the C++0x Standard Draft.
Will the concepts branch be discontinued?

Re: The future of concepts

[James Dennett]

On Tue, Jul 28, 2009 at 3:01 AM, Piotr Wyderski<piotr.wyderski@gmail.com> wrote:
> Concepts have recently been removed from the C++0x Standard Draft.
> Will the concepts branch be discontinued?

I hope not.  Concepts will be "finished" and re-added to C++, and it
would be immensely helpful in that effort if there were a version of
g++ with stronger Concepts support than ConceptGCC had.

-- James

Re: The future of concepts

[Ed Smith-Rowland]

James Dennett wrote:
> On Tue, Jul 28, 2009 at 3:01 AM, Piotr Wyderski<piotr.wyderski@gmail.com> wrote:
>   
>> Concepts have recently been removed from the C++0x Standard Draft.
>> Will the concepts branch be discontinued?
>>     
>
> I hope not.  Concepts will be "finished" and re-added to C++, and it
> would be immensely helpful in that effort if there were a version of
> g++ with stronger Concepts support than ConceptGCC had.
>
> -- James
>
>   
We need a gcc branch for concepts.  One of the major complaints on 
concepts and one of the major contributors to its being dropped is that 
there is no implementation experience.  There was no implementation of 
sufficient quality and availability to give compiler developers 
confidence and point to wrinkles in the definition and users time to 
learn and play.  It will take a good couple of years to get one working.

That leaves open the question of whether the ConceptGCC branch is the 
one.  I just don't know.  Maybe someone should start over.  I think aim 
for simplicity.  That was another issue I think: 
http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2009/n2906.pdf     
(Stroustrup)

Ed

Re: The future of concepts

[Basile STARYNKEVITCH]

Ed Smith-Rowland wrote:
> James Dennett wrote:
>> On Tue, Jul 28, 2009 at 3:01 AM, Piotr 
>> Wyderski<piotr.wyderski@gmail.com> wrote:
>>  
>>> Concepts have recently been removed from the C++0x Standard Draft.
>>> Will the concepts branch be discontinued?
>>>     
>>
>> I hope not.  Concepts will be "finished" and re-added to C++, and it
>> would be immensely helpful in that effort if there were a version of
>> g++ with stronger Concepts support than ConceptGCC had.
>>
>> -- James
>>
>>   
> We need a gcc branch for concepts.  One of the major complaints on 
> concepts and one of the major contributors to its being dropped is that 
> there is no implementation experience.  

It could perhaps be not a branch, but a plugin, but I know not much 
about C++ concepts, and absolutely nothing about the existing C++ 
concepts branch[es].

My belief is that making such code a plugin and not a branch would make 
both the plugin feature and the experimental language feature (concepts) 
more popular. And perhaps maintaining a plugin could mean less work than 
maintaing an entire branch.

Regards.

-- 
Basile STARYNKEVITCH         http://starynkevitch.net/Basile/
email: basile<at>starynkevitch<dot>net mobile: +33 6 8501 2359
8, rue de la Faiencerie, 92340 Bourg La Reine, France
*** opinions {are only mines, sont seulement les miennes} ***

Re: The future of concepts

[Jonathan Wakely]

2009/7/28 Basile STARYNKEVITCH:
>
> It could perhaps be not a branch, but a plugin, but I know not much about
> C++ concepts, and absolutely nothing about the existing C++ concepts
> branch[es].

I don't think that would work - the standard library changes that go
along with the language feature could not be implemented as a plugin.
A branch seems like the right way to do it.

Jonathan

Re: The future of concepts

[Jason Merrill]

On 07/28/2009 10:47 AM, Ed Smith-Rowland wrote:
> We need a gcc branch for concepts.

Probably, if someone is working on them, just as for any ongoing project.

> That leaves open the question of whether the ConceptGCC branch is the
> one.

No.  Doug felt that much of ConceptGCC needed to be rewritten; the 
ConceptGCC branch is just a place to store the existing work for later 
reference.

There is a cxx0x-concepts-branch, but no work has been done on it. 
Probably when someone starts serious work on reimplementing concepts 
we'll create a new branch.  I don't currently have any plans to work on 
concepts, as there are plenty of other things to work on that will be in 
C++0x.

Jason

Re: The future of concepts

[Ed Smith-Rowland]

Jason Merrill wrote:
> On 07/28/2009 10:47 AM, Ed Smith-Rowland wrote:
>> We need a gcc branch for concepts.
>
> Probably, if someone is working on them, just as for any ongoing project.
>
>> That leaves open the question of whether the ConceptGCC branch is the
>> one.
>
> No.  Doug felt that much of ConceptGCC needed to be rewritten; the 
> ConceptGCC branch is just a place to store the existing work for later 
> reference.
That effort did look dead.  It seemed to me like a clean slate would be 
nice.

One idea I had was to look at the metaprogramming pseudo concepts that 
seem to be in the library already and beefing those up.  Maybe that plus 
a tiny amount of core language secret sauce would be the best approach 
for concepts.
>
> There is a cxx0x-concepts-branch, but no work has been done on it. 
> Probably when someone starts serious work on reimplementing concepts 
> we'll create a new branch.  I don't currently have any plans to work 
> on concepts, as there are plenty of other things to work on that will 
> be in C++0x.
I agree.  There's constexpr, lambdas, nullptr, etc.

Then there's library stuff like regex mostly.

I was thinking we'd have a lot of green check marks for most of C++-0x 
when it finally comes out.  I think other compilers will too.  There 
won't be hardly any latency at all between ratification and good and 
broad support for C++-0x.  That's nothing to sneeze at.
>
> Jason
>