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  • What new Unicode functions are there in C++0x?

    - by luiscubal
    It has been mentioned in several sources that C++0x will include better language-level support for Unicode(including types and literals). If the language is going to add these new features, it's only natural to assume that the standard library will as well. However, I am currently unable to find any references to the new standard library. I expected to find out the answer for these answers: Does the new library provide standard methods to convert UTF-8 to UTF-16, etc.? Does the new library allowing writing UTF-8 to files, to the console (or from files, from the console). If so, can we use cout or will we need something else? Does the new library include "basic" functionality such as: discovering the byte count and length of a UTF-8 string, converting to upper-case/lower-case(does this consider the influence of locales?) Finally, are any of these functions are available in any popular compilers such as GCC or Visual Studio? I have tried to look for information, but I can't seem to find anything? I am actually starting to think that maybe these things aren't even decided yet(I am aware that C++0x is a work in progress).

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  • C++0x and the Lack of Polymorphic Lambdas - Why?

    - by Dominar
    I've been reviewing the draft version of the upcoming C++0x standard. Specifically the section on lambdas, and am confused as to the reasoning for not introducing polymorphic lambdas. I had hoped we could use code such as the following: template<typename Container> void foo(Container c) { for_each(c.begin(),c.end(),[](T& t) { ++t; }); } What were the reasons: Was it the committee ran out of time? That polymorphic lambdas are too hard to implement? Or perhaps that they are seen as not being needed by the PTB?

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  • Can I upgrade Xcode to support a newer version of GCC to learn C++0x?

    - by Shane
    I would like to jump in learn C++0x, which has matured to a level I'm happy with. Xcode on Snow Leopard 10.6 is currently at GCC 4.2.1, and the new features I'd like to try, like std::shared_ptr, lambdas, auto, null pointer constant, unicode string literals, and other bits and pieces, require at least 4.3 (I believe). Ideally I'd use Xcode but I'm not even sure if you can manually upgrade the compiler for Xcode. Is this possible? Otherwise, what is the best way to install a different version of GCC that doesn't interfere with the rest of the system? Regards, Shane

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  • How do you use C++0x raw strings with GCC 4.5?

    - by Rob N
    This page says that GCC 4.5 has C++ raw string literals: http://gcc.gnu.org/projects/cxx0x.html But when I try to use the syntax from this page: http://www2.research.att.com/~bs/C++0xFAQ.html#raw-strings #include <iostream> #include <string> using namespace std; int main() { string s = R"[\w\\\w]"; } I get this error: /opt/local/bin/g++-mp-4.5 -std=gnu++0x -O3 rawstr.cc -o rawstr rawstr.cc:9:19: error: invalid character '\' in raw string delimiter rawstr.cc:9:5: error: stray 'R' in program What is the right syntax for raw strings?

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  • Why timed lock doesnt throws a timeout exception in C++0x?

    - by Vicente Botet Escriba
    C++0x allows to lock on a mutex until a given time is reached, and return a boolean stating if the mutex has been locked or not. template <class Clock, class Duration> bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time); In some contexts, I consider an exceptional situation that the locking fails because of timeout. In this case an exception should be more appropriated. To make the difference a function lock_until could be used to get a timeout exception when the time is reached before locking. template <class Clock, class Duration> void lock_until(const chrono::time_point<Clock, Duration>& abs_time); Do you think that lock_until should be more adequate in some contexts? if yes, on which ones? If no, why try_lock_until will always be a better choice?

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  • Are function-local typedefs visible inside C++0x lambdas?

    - by GMan - Save the Unicorns
    I've run into a strange problem. The following simplified code reproduces the problem in MSVC 2010 Beta 2: template <typename T> struct dummy { static T foo(void) { return T(); } }; int main(void) { typedef dummy<bool> dummy_type; auto x = [](void){ bool b = dummy_type::foo(); }; // auto x = [](void){ bool b = dummy<bool>::foo(); }; // works } The typedef I created locally in the function doesn't seem to be visible in the lambda. If I replace the typedef with the actual type, it works as expected. Here are some other test cases: // crashes the compiler, credit to Tarydon int main(void) { struct dummy {}; auto x = [](void){ dummy d; }; } // works as expected int main(void) { typedef int integer; auto x = [](void){ integer i = 0; }; } I don't have g++ 4.5 available to test it, right now. Is this some strange rule in C++0x, or just a bug in the compiler? From the results above, I'm leaning towards bug. Though the crash is definitely a bug. For now, I have filed two bug reports. All code snippets above should compile. The error has to do with using the scope resolution on locally defined scopes. (Spotted by dvide.) And the crash bug has to do with... who knows. :) Update According to the bug reports, they have both been fixed for the next release of Visual Studio 2010.

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  • Why there is no scoped locks for multiple mutexes in C++0x or Boost.Thread?

    - by Vicente Botet Escriba
    C++0x thread library or Boost.thread define non-member variadic template function that lock all lock avoiding dead lock. template <class L1, class L2, class... L3> void lock(L1&, L2&, L3&...); While this function avoid help to deadlock, the standard do not includes the associated scoped lock to write exception safe code. { std::lock(l1,l2); // do some thing // unlock li l2 exception safe } That means that we need to use other mechanism as try-catch block to make exception safe code or define our own scoped lock on multiple mutexes ourselves or even do that { std::lock(l1,l2); std::unique_lock lk1(l1, std::adopted); std::unique_lock lk2(l2, std::adopted); // do some thing // unlock li l2 on destruction of lk1 lk2 } Why the standard doesn't includes a scoped lock on multiple mutexes of the same type, as for example { std::array_unique_lock<std::mutex> lk(l1,l2); // do some thing // unlock l1 l2 on destruction of lk } or tuples of mutexes { std::tuple_unique_lock<std::mutex, std::recursive_mutex> lk(l1,l2); // do some thing // unlock l1 l2 on destruction of lk } Is there something wrong on the design?

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  • Will C++0x support __stdcall or extern "C" capture-nothing lambdas?

    - by Daniel Trebbien
    Yesterday I was thinking about whether it would be possible to use the convenience of C++0x lambda functions to write callbacks for Windows API functions. For example, what if I wanted to use a lambda as an EnumChildProc with EnumChildWindows? Something like: EnumChildWindows(hTrayWnd, CALLBACK [](HWND hWnd, LPARAM lParam) { // ... return static_cast<BOOL>(TRUE); // continue enumerating }, reinterpret_cast<LPARAM>(&myData)); Another use would be to write extern "C" callbacks for C routines. E.g.: my_class *pRes = static_cast<my_class*>(bsearch(&key, myClassObjectsArr, myClassObjectsArr_size, sizeof(my_class), extern "C" [](const void *pV1, const void *pV2) { const my_class& o1 = *static_cast<const my_class*>(pV1); const my_class& o2 = *static_cast<const my_class*>(pV2); int res; // ... return res; })); Is this possible? I can understand that lambdas that capture variables will never be compatible with C, but it at least seems possible to me that capture-nothing lambdas can be compatible.

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  • C++0x implementation guesstimates?

    - by dsimcha
    The C++0x standard is on its way to being complete. Until now, I've dabbled in C++, but avoided learning it thoroughly because it seems like it's missing a lot of modern features that I've been spoiled by in other languages. However, I'd be very interested in C++0x, which addresses a lot of my complaints. Any guesstimates, after the standard is ratified, as to how long it will take for major compiler vendors to provide reasonably complete, production-quality implementations? Will it happen soon enough to reverse the decline in C++'s popularity, or is it too little, too late? Do you believe that C++0x will become "the C++" within a few years, or do you believe that most people will stick to the earlier standard in practice and C++0x will be somewhat of a bastard stepchild, kind of like C99?

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  • Configuring gcc compiler switches in Qt / QtCreator / QMake

    - by andand
    I recently tried to use Qt Creator 1.3.2 / Qt 4.6.2 / gcc 4.4.0 (32-bit version) on Windows 7 (64-bit) to compile an application using some of the experimental C++0x extensions and encountered the following (fatal) error: This file requires compiler and library support for the upcoming ISO C++ standard, C++0x. This support is currently experimental, and must be enabled with the -std=c++0x or -std=gnu++0x compiler options. In my search for a solution, I came across this thread, and added the following to the .pro file: CXXFLAGS += -std=c++0x but that didn't seem to make a difference. So, I expect there's some tag I need to add to the .pro (project) file, but I've never messed with the gcc compiler switches in Qt / QMake / QtCreator before, and am uncertain about the proper invokation / incantation. So, my question is how do you set gcc compiler switches when using QtCreator / QMake / Qt?

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  • C++0x: How can I access variadic tuple members by index at runtime?

    - by nonoitall
    I have written the following basic Tuple template: template <typename... T> class Tuple; template <uintptr_t N, typename... T> struct TupleIndexer; template <typename Head, typename... Tail> class Tuple<Head, Tail...> : public Tuple<Tail...> { private: Head element; public: template <uintptr_t N> typename TupleIndexer<N, Head, Tail...>::Type& Get() { return TupleIndexer<N, Head, Tail...>::Get(*this); } uintptr_t GetCount() const { return sizeof...(Tail) + 1; } private: friend struct TupleIndexer<0, Head, Tail...>; }; template <> class Tuple<> { public: uintptr_t GetCount() const { return 0; } }; template <typename Head, typename... Tail> struct TupleIndexer<0, Head, Tail...> { typedef Head& Type; static Type Get(Tuple<Head, Tail...>& tuple) { return tuple.element; } }; template <uintptr_t N, typename Head, typename... Tail> struct TupleIndexer<N, Head, Tail...> { typedef typename TupleIndexer<N - 1, Tail...>::Type Type; static Type Get(Tuple<Head, Tail...>& tuple) { return TupleIndexer<N - 1, Tail...>::Get(*(Tuple<Tail...>*) &tuple); } }; It works just fine, and I can access elements in array-like fashion by using tuple.Get<Index() - but I can only do that if I know the index at compile-time. However, I need to access elements in the tuple by index at runtime, and I won't know at compile-time which index needs to be accessed. Example: int chosenIndex = getUserInput(); cout << "The option you chose was: " << tuple.Get(chosenIndex) << endl; What's the best way to do this?

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  • Is Boost.Tuple compatible with C++0x variadic templates ?

    - by Thomas Petit
    Hi, I was playing around with variadic templates (gcc 4.5) and hit this problem : template <typename... Args> boost::tuple<Args...> my_make_tuple(Args... args) { return boost::tuple<Args...>(args...); } int main (void) { boost::tuple<int, char> t = my_make_tuple(8, 'c'); } GCC error message : sorry, unimplemented: cannot expand 'Arg ...' into a fixed-length argument list In function 'int my_make_tuple(Arg ...)' If I replace every occurrence of boost::tuple by std::tuple, it compiles fine. Is there a problem in boost tuple implementation ? Or is this a gcc bug ? I must stick with Boost.Tuple for now. Do you know any workaround ? Thanks.

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  • Why is there a sizeof... operator in C++0x?

    - by Motti
    I saw that @GMan implemented a version of sizeof... for variadic templates which (as far as I can tell) is equivalent to the built in sizeof.... Doesn't this go against the design principle of not adding anything to the core language if it can be implemented as a library function[citation needed]?

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  • What is the motivation behind c++0x lambda expressions?

    - by LoudNPossiblyRight
    I am trying to find out if there is an actual computational benefit to using lambda expressions in c++, namely "this code compiles/runs faster/slower because we use lambda expressions" OR is it just a neat development perk open for abuse by poor coders trying to look cool? Thanks. PS. I understand this question may seem subjective but i would much appreciate the opinion of the community on this matter.

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  • How to enable nullptr from C++0x in the Visual C++ 2010?

    - by Sorin Sbarnea
    I wonder how can I enable the nullptr in the just released Visual Studio 2010. (C++ project, not managed). This is one of the new features but it is not available by default and looking inside the documentation at http://msdn.microsoft.com/en-us/library/4ex65770(VS.100).aspx it seams that it is enabled by /clr but this is managed! Is this a feature added only for .NET?

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  • How do i use 'auto' in C++ (C++0x) ?

    - by LoudNPossiblyRight
    What do i have to do to this code to make it compile, it's braking around this line: auto val = what.getObject(); #include<iostream> using namespace std; class CUP{ public: void whatsHappening(){} }; class MUG{ public: void whatsHappening(){} }; class CupThrower{ public: CUP cp; CUP getObject(){ return cp;} }; class MugThrower{ public: MUG mg; MUG getObject(){return mg;} }; template <typename T> void whatsHappening(T what){ auto val = what.getObject(); //DOES NOT COMPILE val.whatsHappening(); } int main(){ CupThrower ct; MugThrower mt; whatsHappening(ct); whatsHappening(mt); return 0; } i am using VS2008 to compile.

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  • C++0x, How do I expand a tuple into variadic template function arguments?

    - by Gustaf
    Consider the case of a templated function with variadic template arguments: template<typename Tret, typename... T> Tret func(const T&... t); Now, I have a tuple t of values. How do I call func() using the tuple values as arguments? I've read about the bind() function object, with call() function, and also the apply() function in different some now-obsolete documents. The GNU GCC 4.4 implementation seems to have a call() function in the bind() class, but there is very little documentation on the subject. Some people suggest hand-written recursive hacks, but the true value of variadic template arguments is to be able to use them in cases like above. Does anyone have a solution to is, or hint on where to read about it?

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