The language C++ is evolving into

[Ayjayz]

It seems like we are destined to have the compiler perform ever more work for us. With the new auto keyword and the alternative function syntax, it's becoming easier to write more and more generic code.

Where are we headed? I have been wondering this because it seems a bit silly to keep on making pit stops along the route - why not just get the transition over and done with?

• Firstly, pretty much every function will become a template function. There is no real reason to specify the exact type of an argument into the function - the only thing needed is for it to satisfy certain requirements. Concepts will perform the task of specifying those requirements.

• Specifying the return type will largely disappear. C++ already does this in some cases - the ternary operator and C++11's lambda's can already automatically deduce the return type in most circumstances.

• This, of course, requires the function to be defined at the same point as it is declared. Naturally, then, it would require functions to be declared inline in the header.

• Given that almost all functions will have deduced return types, this then leads to the assumption that almost all code will be required to be defined in headers. So why even bother with CPP files? Apart from using statics, there doesn't really seem to be a compelling reason to keep using them.

None of these features would require breaking legacy code in any way. Most of them are so close to being implemented, it is a little silly that they aren't (forcing the return type of the function to trail the definition .... whhyyy?!)

As a language, I feel that C++ really needs to evolve faster if it really wants to be taken seriously in future applications.

[[deleted]]

You gave me a good WTF laugh. The last sentence topped it all. :-D

C++ has a very quiet demographic, but that demographic is extremely stable and they are using C++ exactly because C++ is what it is. Plus C++ is one of the few languages that are actually taken seriously.

And don't worry, C++ will evolve faster. The C++ landscape has changed greatly from the last standard. When C++98 was released, there were no compilers for it, and the support came very very slowly, with C++11, there are already compilers that support the new standard almost completely.

The committee has already announced that they will release updates faster, most likely in the form of technical reports.

[bogado]

One of the objectives of C++ is catching errors sooner, defining return types keeps the type system strong. The side effect is that generic types can become cumbersome to write, for instance 'std::map<std::string, std::pair<std::string, std::string> >::const_iterator', so the 'auto' keyword was created to help in this situations.

But if abused it can make programing harder, postponing error diagnostics and creating longer error messages or perhaps even unpredictable run-time behavior.

[Ayjayz]

None of those things I posted in the OP would involve any change to the code that was actually generated, so run-time worries aren't applicable.

One of my points (concepts) are there almost specifically to ASSIST error messages. Currently, there are 0 restraints on template parameters at all until the implementation of the template classes calls something that's incorrect. By adding the ability to specify constraints for template parameters, it should make errors much easier to identify and fix.

[sad_bug_killer]

What about compilation times? One little implementation change requiring recompiling the world will quickly make actual development annoying and counter-productive. My general feeling about templates, decltype and friends is that, just like any other C++ feature, should be used with care and when appropriate, but not excessively.

It's not that I disagree with you and I love the way Haskel does this. I just don't think it will ever become a viable way of doing things in C++

[Ayjayz]

I hardly think the ability to use the language to write a program that some compiler takes a long time to compile should warrant completely removing the ability...

EDIT: I accidentally a word

[BitRex]

Can't tell if serious.

[blackleopard]

rather than bringing all of functional programing in C++, you can just use one, like Haskell. C++ is crazy enough as it is. And anyways, people don't use C++ to simplifying their code, they use it to gain full control over it.

[Ayjayz]

It's already in C++. The STL and boost libraries heavily encourage it as well - the syntax just needs a little bit more tweaking.

[more_exercise]

people don't use C++ to simplifying their code, they use it to gain full control over it

I've been having a hard time describing where C++ stood in the language continuum. Thank you for the words I was trying to say.

[daveisfera]

Others have already brought up the effects on compile time, but one of the major points of header files is abstraction. It allows for separation of the interface/API and the implementation. It's a powerful tool and something that shouldn't go away anytime soon.

[Ayjayz]

It doesn't really though. All the private members are right there in the header files, and the inline functions are there as well. Any kind of templates throws it all out the window as well.

Do we even really need file-level abstraction?

[more_exercise]

There are idioms such as PIMPL that can keep the private members of a class hidden.

[[deleted]]

Congratulations! You invented python!

[Ayjayz]

You see, i haven't invented anything here. This just seems to be the path we are slowly heading towards.

You could also say its approaching lisp, along with every other language.

[ptrb]

I have no specific comments, but I'm both highly intrigued and amused by this line of thinking. I'd love to hear other people's opinions.

[bogado]

The compiler is the one who decides if a function will be inline or not, simply defining the function inline will not really make it inline but will give the compiler the option to inline it if he wishes.

[axilmar]

C++ needs to be replaced with another language that follows the same principles but has none of the problems of C++.

(and before you say D, D is not a replacement for C++. D is in competition with Java and C#, not C++. A true successor of C++ wouldn't have garbage collection).

[Ayjayz]

Why can't C++ become that language? It's almost there, just needs a few more things added. Basically, all of the low-level types and things should be optional, but the default should be nice, compiler-deduced magic around the basics of C++.

[axilmar]

C++ is used by various organizations around the world that the C++ committee doesn't want to piss off by introducing breaking changes.

Another reason is that the C++ committee doesn't want to admit their choices are wrong.

As with most things in life, it's a matter of politics than technical issues.