C++ Creator Wants To Solve 35-Year-Old Generic Programming Issues With Concepts (cio.com)

C++ creator Bjarne Stroustrup is arguing that we can improve code by grounding generic programming in concepts -- what's required by a template's arguments. An anonymous reader quotes Paul Krill's report on a new paper by Stroustrup: In concepts, Stroustrup sees the solution to the interface specification problem that has long dogged C++, the language he founded more than 35 years ago. "The way we write generic code today is simply too different from the way we write other code," Stroustrup says... Currently an ISO technical specification, concepts provide well-specified interfaces to templates without runtime overhead. Concepts, Stroustrup writes, are intended to complete C++'s support for generic programming as initially envisioned. "The purpose of concepts is to fundamentally simplify and improve design. This leads to fewer bugs and clearer -- often shorter -- code"...

Concepts, Stroustrup believes, will greatly ease engineers' ability to write efficient, reliable C++ code... The most obvious effect will be a massive improvement in the quality of error messages, but the most important long-term effect will be found in the flexibility and clarity of code, Stroustrup says. "In particular, having well-specified interfaces allows for simple, general and zero-overhead overloading of templates. That simplifies much generic code"
Concepts are already available in GNU C Compiler 6.2, and Stroustrup wants them to be included in C++ 20. "In my opinion, concepts should have been part of C++ 17, but the committee couldn't reach consensus on that."

Comments

Re:how about modules?

[Anonymous Coward]

Really. After doing a little Ada programming, or even java with interfaces, not having a hard separation between interface and implementation is infuriating.

Re:As someone with a masters in this -exact field-

[slew]

Richard Feynman and Albert Einstein both did exactly this. You really can't understand quantum mechanics or general relativity without math. You can think you do, and both of them were great at providing simple explanations that gave the illusion of understanding... but it was only an illusion, which of course they knew perfectly well.

I don't know about Einstein, but Feynman was also good at explaining things using math in a way that gave a typical physics student the illusion that you understood it. But that was only an illusion, as when you got back to your dorm room to do the homework you realized that he explained it in a way that you could not replicate because to him the math (usually path integrals) was so intuitive that he could breeze through it on the chalkboard, but you would actually have to grunge out the calculus because of your relative ignorance. Even the TAs weren't able to help you understand it the way he explained, but they would usually also have to grunge out the math to explain it to you.

It was then you realized that not only was he good at explaining things at a high level that gave you the illusion of understanding, but he knew the stuff so thoroughly in a way that you only wish you could understood it, someday.

Even in Physics X, he always had a few mathematical gems that seemed completely unrecreatable outside the lecture room. And if you ever heard him describe his techniques to pickup women, well, those were also something you might think you understand, but were totally unable to replicate later either... ;^)

Re:More features.

[TheRaven64]

Really? Prior to 1998, there was no standard library, though the Standard Template Library from SGI was pretty much treated as the standard library. When C++ was standardised in 1998, most of the STL was incorporated into the C++ standard library, so almost everything that you'd learned from the STL would still be relevant. The next bump to the standard was in 2011. Lots of stuff was added to the standard library, but very few things were changed in incompatible ways (auto_ptr was deprecated, because in 13 years no one had figured out how to use it without introducing more problems than it solved) and almost all C++98 code compiles without problems against a C++11 library. C++14 and C++17 have both added a lot more useful things but removed or made incompatible changes to very few things.

Let's look at a commonly used class, std::vector. The only incompatible changes in the last 18 years have been subtle changes to how two of the types that are accessible after template instantiation are defined. Code using these types will still work (because the changes are not on the public side of the interface), but the chain for defining them is more explicit (e.g. the type of elements is now the type of elements, not the type of things allocated by the thing that allocates references - code would fail to compile if these weren't the same type). The changes in std::map are the same.

That said, you do need to learn new things. Modern C++ shouldn't use bare pointers anywhere and should create objects with std::make_shared or std::make_unique. The addition of std::variant, std::optional, and std::any in C++17 clean up a lot of code.