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  • C++, LHS state after exception is thrown

    - by aaa
    hi. I am learning C++ exceptions and I would like some clarification of the scenario: T function() throws(std::exception); ... T t = value; try { t = function(); } catch (...) {} if the exception is thrown, what is the state of variable t? unchanged or undefined?

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  • C++ domain specific embedded language operators

    - by aaa
    hi. In numerical oriented languages (Matlab, Fortran) range operator and semantics is very handy when working with multidimensional data. For example: A(i:j,k,:n) // represents two-dimensional slice B(i:j,0:n) of A at index k unfortunately C++ does not have range operator (:). of course it can be emulated using range/slice functor, but semantics is less clean than Matlab. I am prototyping matrix/tensor domain language in C++ and am wondering if there any options to reproduce range operator. I still would like to rely on C++/prprocessor framework exclusively. So far I have looked through boost wave which might be an suitable option. is there any other means to introduce new operators to C++ DSL?

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  • Which namespace does operator<< (stream) go to?

    - by aaa
    If I have have some overloaded ostream operators, defined for library local objects, is its okay for them to go to std namespace? If I do not declare them in std namespace, then I must use using ns:: operator <<. As a possible follow-up question, are there any operators which should go to standard or global namespace?

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  • boost::enable_if class template method

    - by aaa
    I got class with template methods that looks at this: struct undefined {}; template<typename T> struct is_undefined : mpl::false_ {}; template<> struct is_undefined<undefined> : mpl::true_ {}; template<class C> struct foo { template<class F, class V> typename boost::disable_if<is_undefined<C> >::type apply(const F &f, const V &variables) { } template<class F, class V> typename boost::enable_if<is_undefined<C> >::type apply(const F &f, const V &variables) { } }; apparently, both templates are instantiated, resulting in compile time error. is instantiation of template methods different from instantiation of free functions? I have fixed this differently, but I would like to know what is up. Thank you

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  • C++ boost ublas + units dimension constraints

    - by aaa
    hello. I am seeking advice on design/general idea on how to force matrix dimension constraints on ublas matrix/vector possibly using boost units. For example, let matrix A have dimensions of time x force (for example) // does not have dimensions, time x force and force x time are not distinguished. matrix<double> A; //something like? dimension<time, force, matrix<double> > A; dimension<force, time, matrix<double> > B = trans(A); have you done something like this or do you have some good idea about how to organize such constraints? Thank you

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  • C++ performance, for versus while

    - by aaa
    hello. In general (or from your experience), is there difference in performance between for and while loops? What if they are doubly/triply nested? Is vectorization (SSE) affected by loop variant in g++ or Intel compilers? Thank you

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  • When to choose C over C++?

    - by aaa
    Hi. I have become a fond of C++ thanks to this website. Before, I programmed exclusively in C/Fortran, thinking that C++ was too slow (not anymore). Is there a reason to write new project purely in C? this is besides obvious things like low-level kernel/system components. What about intermediate things, like communication libraries, for example MPI? Is C still more portable than C++? I have messed with pretty exotic systems, like Cray, but have yet to see non-embedded system without C++. thanks

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  • Multithreading, when to yield versus sleep

    - by aaa
    hello. To clarify terminology, yield is when thread gives up its time slice. My platform of interest is POSIX threads, but I think question is general. Suppose I have consumer/producer pattern. If I want to throttle either consumer or producer, which is better to use, sleep or yield? I am mostly interested in efficiency of using either function. Thanks

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  • C++ catch constructor exception

    - by aaa
    hi. I do not seem to understand how to catch constructor exception. Here is relevant code: struct Thread { rysq::cuda::Fock fock_; template<class iterator> Thread(const rysq::cuda::Centers &centers, const iterator (&blocks)[4]) : fock_() { if (!fock_) throw; } }; Thread *ct; try { ct = new Thread(centers_, blocks); } catch(...) { return false; } // catch never happens, So catch statement do not execute and I get unhandled exception. What did I do wrong? this is straight C++ using g++.

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  • C++ template parameter/class ambiguity

    - by aaa
    hello. while testing with different version of g++, the following problem came up template<class bra> struct Transform<bra, void> : kernel::Eri::Transform::bra { static const size_t ni = bra::A::size; bra::A is interpreted as kernel::Eri::Transform::bra::A, rather than template argument by g++ 4.1.2. on the other hand, g++ 4.3 gets it right. what should be correct behavior according to standard? Meanwhile, I refactor slightly to make problem go away.

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  • C++ CRTP(template pattern) question

    - by aaa
    following piece of code does not compile, the problem is in T::rank not be inaccessible (I think) or uninitialized in parent template. Can you tell me exactly what the problem is? is passing rank explicitly the only way? or is there a way to query tensor class directly? Thank you #include <boost/utility/enable_if.hpp> template<class T, // size_t N, class enable = void> struct tensor_operator; // template<class T, size_t N> template<class T> struct tensor_operator<T, typename boost::enable_if_c< T::rank == 4>::type > { tensor_operator(T &tensor) : tensor_(tensor) {} T& operator()(int i,int j,int k,int l) { return tensor_.layout.element_at(i, j, k, l); } T &tensor_; }; template<size_t N, typename T = double> // struct tensor : tensor_operator<tensor<N,T>, N> { struct tensor : tensor_operator<tensor<N,T> > { static const size_t rank = N; }; I know the workaround, however am interested in mechanics of template instantiation for self-education

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  • syntax to express mathematical formula concisely in your language of choice

    - by aaa
    hello. I am developing functional domain specific embedded language within C++ to translate formulas into working code as concisely and accurately as possible. Right now my language looks something like this: // implies two nested loops j=0:N, i=0,j (range(i) < j < N)[T(i,j) = (T(i,j) - T(j,i))/e(i+j)]; // implies summation over above expression sum(range(i) < j < N))[(T(i,j) - T(j,i))/e(i+j)]; I am looking for possible syntax improvements/extensions or just different ideas about expressing mathematical formulas as clearly and precisely as possible. Can you give me some syntax examples relating to my question which can be accomplished in your language of choice which consider useful. In particular, if you have some ideas about how to translate the above code segments, I would be happy to hear them Thank you

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  • C++ auto function return type implementation

    - by aaa
    hello. Is there macro, something like BOOST_AUTO, which would allow to emulate automatic return type deduction of function in C++? I mean something like trailing-return-type, http://en.wikipedia.org/wiki/C%2B%2B0x#Alternative_function_syntax thank you

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  • UV-vis detector [Hardware]

    - by aaa
    hello. This is not hundred percent programming related question, but I was not able to find answer on the net. Is there some kind of detector to record frequency/intensity of light radiation source? something like spectroscopy detector, but instead of actual machine, just the module which can be integrated in project. I have tried searching on Google but I do not even know what such device is called if you know the more appropriate place to ask, can you let me know please. Thank you

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  • C instruction address

    - by aaa
    hello. Disclaimer, I not do anything in particular with regards this question, just curious. Is it possible to take address of instruction or block in C? in essence, is there jump equivalent in C? for example: void function() { int k; { // is a possible to go to this address from arbitrary point in code? int i, j; k += j+i; } } thank you

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  • Is it possible to reinterpret pointer as dimensioned array reference?

    - by aaa
    hi. Suppose I have some pointer, which I want to reinterpret as static dimension array reference: double *p; double (&r)[4] = ?(p); // some construct? // clarify template< size_t N> void function(double (&a)[N]); ... double *p; function(p); // this will not work. // I would like to cast p as to make it appear as double[N] Is it possible to do so? how do I do it?

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  • C++ ambiguous template instantiation

    - by aaa
    the following gives me ambiguous template instantiation with nvcc (combination of EDG front-end and g++). Is it really ambiguous, or is compiler wrong? I also post workaround à la boost::enable_if template<typename T> struct disable_if_serial { typedef void type; }; template<> struct disable_if_serial<serial_tag> { }; template<int M, int N, typename T> __device__ //static typename disable_if_serial<T>::type void add_evaluate_polynomial1(double *R, const double (&C)[M][N], double x, const T &thread) { // ... } template<size_t M, size_t N> __device__ static void add_evaluate_polynomial1(double *R, const double (&C)[M][N], double x, const serial_tag&) { for (size_t i = 0; i < M; ++i) add_evaluate_polynomial1(R, C, x, i); } // ambiguous template instantiation here. add_evaluate_polynomial1(R, C, x, serial_tag());

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  • C++ compilers and back/front ends

    - by aaa
    Hello. for my own education I am curious what compilers use which C++ front-end and backend. Can you enlighten me where the following technologies are used and what hallmarks/advantages they have if any? Open64 - is it backend, front-end, or both? Which compilers use it? I encounter it in cuda compiler. EDG - as far as I can tell this is a backend use by Intel compilers and Comeau. do other compilers use it? I found quite a few references to it in boost source code. ANTLR - this is general parser. Do any common compilers use it? Regarding compilers: with front-end/backend does gcc compiler suite uses? does it have common heritage with any other compiler? what front-end/backend PGI and PathScale compilers use? what front-end/backend XL compiler uses (IBM offering). Thanks.

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  • C++ constant reference lifetime

    - by aaa
    hello I have code that looks like this: class T {}; class container { const T &first, T &second; container(const T&first, const T & second); }; class adapter : T {}; container(adapter(), adapter()); I thought lifetime of constant reference would be lifetime of container. However, it appears otherwise, adapter object is destroyed after container is created, leading dangling reference. What is the correct lifetime? how to correctly implement binding temporary object to class member reference? Thanks

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  • why i cant read my webservice with jquery???

    - by rima
    what's my function problem?I wana read from my webservice but I just receive error :( the browser message is: "undefined- status:error" when I press button just I see the error function of my Jqueary calling but I dont know why??plz help me. function SetupCompanyInfo(companyID) { //alert('aaa'); companyID = '1'; $.ajax({ type: "POST", url: '../../../Services/CompanyServices.asmx/GetCompanyInfo', data: "{}", contentType: "application/json; charset=utf-8", dataType: "json", success: OnSuccess, error: OnError }); } function OnSuccess(data, status) { SetMainBody(data); } function OnError(request, status, error) { SetMainBody(error + '- ' + request + ' status:' + status); } my webservice: using System; using System.Web.Services; using System.Web.Script.Services; /// <summary> /// Summary description for CompanyServices /// </summary> [WebService(Namespace = "http://tempuri.org/")] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] [ScriptService] //[System.ComponentModel.ToolboxItem(false)] public class CompanyServices : System.Web.Services.WebService { [WebMethod] public string GetCompanyInfo() { string response = "aaa"; Console.WriteLine("here"); return response.ToString(); } [WebMethod] public string GetCompanyInfo(string id) { string response = "aaa"; Console.WriteLine("here2"+id); return response.ToString(); } } my aspx file,part of head and my button code: <script src="../../Scripts/InnerFunctions.js" type="text/javascript"></script> <script src="../../Scripts/jquery-1.3.2.min.js" type="text/javascript"></script> <script src="../../Scripts/TabMenu.js" type="text/javascript"></script> <script src="Scripts/InternalFunctions.js" type="text/javascript"></script> <div dir="rtl" style="border: 1px solid #CCCCCC"> <asp:Image ID="Image1" runat="server" ImageUrl="../../generalImg/Icons/64X64/settings_Icon_64.gif" style="width: 27px; height: 26px" onclick="SetupCompanyInfo(1)" /></div>

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  • C99 variable length automatic array performance

    - by aaa
    Is there significant cpu/memory overhead associated with using automatic arrays with g++/Intel on 64-bit x86 linux platform? int function(int N) { double array[N]; overhead compared to allocating array before hand (assuming function is called multiple times) overhead compared to using new overhead compared to using malloc The range of N may be from 1kb to 16kb roughly, stack overrun is not a problem.

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