Stroustrup Reveals What's New In C++ 11

snydeq writes "Bjarne Stroustrup discusses the latest version of C++, which, although not a major overhaul, offers many small upgrades to appeal to different areas of development. From the interview: 'I like the way move semantics will simplify the way we return large data structures from functions and improve the performance of standard-library types, such as string and vector. People in high-performance areas will appreciate the massive increase in the power of constant expressions (constexpr). Users of the standard library (and some GUI libraries) will probably find lambda expressions the most prominent feature. Everybody will use smaller new features, such as auto (deduce a variable's type from its initializer) and the range-for loop, to simplify code.'"

Comments

"Not a major overhaul"?

[Godai]

I mean, it's not, but it makes it sound like C++11 is a minor update. Lambdas, auto, concurrency, are these minor updates? There's a lot of interesting stuff in C++11!

Re:"Not a major overhaul"?

[genjix]

I've been using the C++11 for 6 months now in my own project (libbitcoin) and the new features and syntax really make your code sharper, clearer and better. C++ is no longer that unsafe language if you know how to code in it properly - you never really have to do any manual memory management if you use shared pointers.

constexpr allowed me to create compile time constants that are the function of a bunch of complicated expressions. Sure, I could just put the result in the code, but by using constexpr (a far more expressive metaprogramming utility than templates) I can document where those constants came from by using code. Neat huh!

Using variadic templates, I was able to write decorators that can be applied to any function. I simply wrap my functions with this class and then its operator() will be called before calling the passed in function object (which I can define using lambdas or std::bind now :)

auto means I no longer have to type std::vector>::iterator in every for loop. Likewise for (const transaction& tx: block.transactions) is much more terse and clearer.

The new features to the standard library are brilliant. Threading has never been easier: std::thread t(foo, x, y); will call foo(x, y) in a new thread. When I decide to finish the threads and then join them I call: t.join(); ... Simple.

As libbitcoin is highly asynchronous, I don't like to use exceptions (which thread does it originate in? where does it get caught? .etc). C++11 now provides the header which defines std::error_code(). An error_code object can be tested as a boolean (to see whether the error is set or not) or compared against an enum value (which you define). They also have an error message (which if you defined the enum value it is set to, you can also set the message), and also you can group different error code values into broader categories! Really useful for asynchronous programming.

std::atomic for a thread-safe counter (useful when you have multiple thread paths executing and want to see when they all finished - increment your counter by one after each path completes) and std::atomic for a thread-safe flag. ... That's off the top of my head. There are dozens of many small things like this. C++ was always my 'native' language, but now it's truly my home.

Re:"Not a major overhaul"?

[19thNervousBreakdown]

Don't forget initializer lists, variadic templates, non-static data member initializers, finally fixing that Template> (note the >>) thing, rvalues, nullptr, strongly-typed enums, constructor improvements (holy god we don't have to rewrite every fucking thing every fucking time or split off into an ::init()), user-defined literals which is crazy cool combined with templates and initializer lists, and lots of stuff I'm sure I'm forgetting about.

Since starting on C#, I've kind of felt like I'm back in the dark ages in C++, even as it remains my favorite language. I've already started using a lot of these improvements, and while C++ still has it's rough edges, the improvement in "fun" while coding is massive. No more for (some_container_type<vector<map<int, string> > >::reverse_iterator aargh = instance.begin(); aargh != instance.end(); ++aargh) for me!

Re:"Not a major overhaul"?

[swillden]

auto means I no longer have to type std vector iterator in every for loop

You didn't anyway. You type in "int" to loop over a vector.

Only if you want to tie yourself to using a vector. Using a proper iterator costs you nothing in code space or execution time (because for a vector it optimizes down to just pointer arithmetic anyway), but means that at some future time you can replace that vector with a different data structure without having to modify the code that operates on it.

Re:News?

[busyqth]

That said, as a professional C++ developer working in HPC, this is exciting.

Stop pretending and get back to your FORTRAN!

and in the next revision...

[busyqth]

S-expressions, continuations, hygenic macros...

Fascinating Software Engineering Challenge

[Bookwyrm]

In some ways, a lot of what is being added to C++ makes me think of Scala, just less readable.

While the additions and extensions certainly make things more interesting and potentially more powerful/easier for the *individual* programmer, I look forward to seeing what sort of interesting train wrecks happen when larger teams try to make use of these features. I certainly hope the debuggers are being updated to be useful when someone's written a template that uses a #define'd macro to specify a closure that is passed through an anonymous function, etc.

This strikes me as the next generation's 'multi-threading' -- where almost every programmer claims they can handle multi-threaded programming, but very few actually do it well. Particularly in teams when interactions require coordination. Going to take a whole new round of winnowing the wheat from the chaff when it comes to finding developers who can actually use these features well without driving their coworkers insane.

Re:I want auto!

[godrik]

chances that oracle will see the light? :-)

Last time they saw the Sun, it did not end well...

Re:In practice it's like a different language.

[tibit]

Now be careful, because inheritance was not really intended for code reuse. If it does help with code reuse, that's a positive consequence, but it's not what inheritance is for, first and foremost. See Liskov substitution principle and all that jazz.

Re:In practice it's like a different language.

[RCL]

So what? STL isn't suited for all possible uses, sometimes you need your own string and container classes.

Don't be a zealot, pragmatic programmer should find the right trade-off between reusing code and writing an optimal one for a specific problem/area. Nothing can be optimal in all cases - sometimes you need to be as close to hardware as possible at the expense of unreadable/inflexible code (for me, those are the most interesting and challenging areas), and sometimes you only care about maintainability of your code by a disposable programming drone.

Re:In practice it's like a different language.

[QuasiEvil]

>Time to join the 21st century grandpa. FILE* leaks.

Hell no. And get off my lawn.

printf() isn't typesafe, but it's a fuckton more readable than all that cout formatting stuff. Also, the fact that it's not typesafe isn't really an issue if you don't suck - trivial unit testing will pretty much show any problems immediately. Besides, gcc/g++ is nice enough to warn you about egregious ones now.

FILE* leaks? I assume by this you mean when sloppy programmers fail to close their files and you start burning through file descriptors. Sounds like a bug to me, and again, stop sucking. Or do what we do - throw an object with a destructor containing fclose() around it. Then you get all the awesomeness of of FILE* (including those awesome formatting commands like fprintf and fscanf) without the danger of your file staying open when something goes nuts.

Why on earth would you want memcpy() to call anything? It's a low level byte move. Anybody with five minutes of familiarity with it should know that. If you wanted something different, use the assignment operator.

void* have all sorts of applications, most recently to me in writing architecture neutral VMs where really all the native machine knows is that it's moving around some sort of pointer.

Now the custom string and array classes? That I'll agree on. Troll on.