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The POCO C++ Libraries Blog

Concepts Removed from C++0x

Filed under: News by alex at 21:45

… which is now C++1x (and hoping x is small number).

Concepts were, in my opinion, really cool feature (types of types) that would have greatly improved template compilation error reporting and also provide help in documenting iterators as well as getting rid of traits. Stroustrup has put 7 years of work into the feature. The door has been left open to introduce them in the next standard, though.

Not the end of the world, but disappointing nevertheless.

The C++0x “Remove Concepts” Decision
Trip Report: Exit Concepts, Final ISO C++ Draft in ~18 Months

I like this part from Sutter:

It’s important to remember that, in 1994, C++ was the only major language whose type genericity capabilities were strong enough to create the Standard Template Library (STL). Today, 15 years later, that is still true; you can’t express the STL’s containers-algorithms design separation well, or at all, using generics facilities in Ada, Java, .NET, or any other significant commercial or research language that I know of; as we learned when doingSTL.NET, you can do the containers well with other generics, but not the orthogonalization with algorithms that is the heart of STL design style. Concepts or not, that hasn’t changed.
So my personal view is that templates have been in the 21st century since about 1994. No other language has yet caught up to their expressive power. And C++0x is adding some further power to templates, in particular by adding variadic templates and template aliases, both of which will help to simplify template code.

Or, as Scott Meyers put it:

In Effective STL (Addison-Wesley, 2001), I wrote, “In the nearly 30 years I’ve been programming, I’ve never seen anything like the STL.” It’s now over 30 years, and I still haven’t.

1 Comment »
  1. I’m shocked I really am.
    a big disappointment

    Comment by MAXAM on July 30, 2009, 00:36

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