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The Removal of Concepts From C++0x

19 replies on 2 pages. Most recent reply: Jul 28, 2009 7:50 PM by Max Lybbert

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Flat View: This topic has 19 replies on 2 pages [ « | 1 2 ]
Achilleas Margaritis

Posts: 674
Nickname: achilleas
Registered: Feb, 2005

Re: The Removal of Concepts From C++0x Posted: Jul 24, 2009 11:22 AM
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> Concepts should allow a diagnostic such as
> "SortedVector<Foo> requires Foo to model the
> LesThanComparable concept" to be given in main(), rather
> than a few levels down in a specific member function.
> That would be one line of error output, not three or more.

The error I showed in the example would be given in main as well.

It does not matter if the error is 3 lines or 1 line, as long as the important line comes first.

John Zabroski

Posts: 272
Nickname: zbo
Registered: Jan, 2007

Re: The Removal of Concepts From C++0x Posted: Jul 27, 2009 11:55 PM
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> > The major advantage of concepts is reduced coupling to
> > type hierarchies, a huge requirement for truly generic
> > programming.
>
> Go on.
>
> Cheers,
> Carson

I highly recommend Lecture Notes in Computer Science 1766: Generic Programming.

In particular, Fundamentals of Generic Programming by Dehnert and Stepanov.

I'm not going to write a ridiculously long rant about why it is so important, though. The literature is there. I am just going to point to it.

Max Lybbert

Posts: 314
Nickname: mlybbert
Registered: Apr, 2005

Re: The Removal of Concepts From C++0x Posted: Jul 28, 2009 4:00 AM
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> From Kalev's article, as quoted above:
>
> As a compromise, the committee decided to pursue the
> refinement of Concepts while leaving the Standard Library
> unconceptualized for the time being.

>
> Really? I see lots of concepts in the October 2008
> working paper, ...
> Since then successive WPs have "conceptualized" additional
> parts of the library as well.

And with this change the committee is reverting to an earlier version of the standard ("We won’t have a de-conceptized working draft for the post-meeting mailing, two weeks after the meeting, but should have one soon after that. ... Recall that, until last September, we had a complete draft of C++0x features specified entirely without the use of concepts. And many of the uses of concepts in the draft standard library were just replacements of preexisting non-concepts wording or implicit requirements ... and will just revert to their previous wording or disappear back into implicitness." http://herbsutter.wordpress.com/2009/07/21/trip-report/ ), because without concepts the portions of the standard that refer to concepts make no sense.

Jonathan Wakely

Posts: 14
Nickname: jwakely
Registered: Jul, 2009

Re: The Removal of Concepts From C++0x Posted: Jul 28, 2009 5:06 AM
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> And with this change the committee is reverting to an
> earlier version of the standard

Right, I was simply pointing out the misinformation in Kalev's article: the library categorically was using concepts in most places, and the feature wasn't pulled because it had been rejected for the library.

Max Lybbert

Posts: 314
Nickname: mlybbert
Registered: Apr, 2005

Re: The Removal of Concepts From C++0x Posted: Jul 28, 2009 7:50 PM
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> > And with this change the committee is reverting to an
> > earlier version of the standard
>
> Right, I was simply pointing out the misinformation in
> Kalev's article: the library categorically was
> using concepts in most places, and the feature wasn't
> pulled because it had been rejected for the library.

Fair enough.

Flat View: This topic has 19 replies on 2 pages [ « | 1  2 ]
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