c++14

问题 To expand flexible function parameters, there is a method using std::initializer_list . However I couldn't understand it. Can anyone explain this in an understandable way? template<typename T, typename... Args> auto print(T value, Args... args) { std::cout << value << std::endl; return std::initializer_list<T>{([&] { std::cout << args << std::endl; }(), value)...}; } 回答1: This is a very confused way of doing things, but C++14 requires that we do something similar. I'll explain the limitations

问题 To expand flexible function parameters, there is a method using std::initializer_list . However I couldn't understand it. Can anyone explain this in an understandable way? template<typename T, typename... Args> auto print(T value, Args... args) { std::cout << value << std::endl; return std::initializer_list<T>{([&] { std::cout << args << std::endl; }(), value)...}; } 回答1: This is a very confused way of doing things, but C++14 requires that we do something similar. I'll explain the limitations

问题 I have the following error in my code: error: allocating an object of abstract class type 'Material' I don't know how to handle this case. I'm aware that std::make_unique performs an allocation, so it can't allocate the object of type Material , but I don't know how to correct it. #include <iostream> #include <memory> struct Material { Material() = default; virtual int get_color() const = 0; }; struct Basic : public Material { Basic() = default; virtual int get_color() const override { return

问题 I have the following error in my code: error: allocating an object of abstract class type 'Material' I don't know how to handle this case. I'm aware that std::make_unique performs an allocation, so it can't allocate the object of type Material , but I don't know how to correct it. #include <iostream> #include <memory> struct Material { Material() = default; virtual int get_color() const = 0; }; struct Basic : public Material { Basic() = default; virtual int get_color() const override { return

问题 CWG 1815 asked (with minor edits): struct A {}; struct B { A&& a = A{}; }; B b1; // #1 B b2{A{}}; // #2 B b3{}; // #3 [...] #2 is aggregate initialization, which binds B::a to the temporary in the initializer for b2 and thus extends its lifetime to that of b2 . #3 is aggregate initialization, but it is not clear whether the lifetime of the temporary in the non-static data member initializer for B::a should be lifetime-extended like #2 or not, like #1 . Per the Notes on that issue, at Issaquah

问题 I have something this: template<typename T> class Image { Image(int w, int h, T defaultVal){ for(int i=0; i<h; i++) for(int j=0; j<w; j++) pixel(j, i) = defaultVal; } template<typename F> Image(int w, int h, F initializer){ for(int i=0; i<h; i++) for(int j=0; j<w; j++) pixel(j, i) = initializer(j, i); } // ... }; My intention is to be able to instantiate an Image like this: Image<int> img0(w, h, 0); // image of zeroes Image<int> imgF(w, h, [](int j, int i){ // checkerboard image return (j/10

问题 I have tried to write a lambda that measures the execution time of arbitrary functions. With a lot of help I have managed that for C++14 and functions having a return value, see Measure execution time of arbitrary functions with C++14 lambda. Then I wanted my code to also work with C++11, therefore I have implemented the same idea with template functions. Finally I have realized that this code does not work for functions having no return value. It has been quite simple to generalize the

问题 I'd like to avoid the duplicates in the code below. #include <iostream> struct Bar{}; template <class... Args> struct FooClass; template <class... Args> inline void foo(Args&&... args) { FooClass<Args...>::impl(std::forward<Args>(args)...); } // Duplicate 1. // Const ref version template <> struct FooClass<Bar const&> { inline static void impl(const Bar& b) { std::cout << "dup1" << std::endl; } }; // Duplicate 2. // Copy version template <> struct FooClass<Bar> { inline static void impl(const

问题 I'd like to avoid the duplicates in the code below. #include <iostream> struct Bar{}; template <class... Args> struct FooClass; template <class... Args> inline void foo(Args&&... args) { FooClass<Args...>::impl(std::forward<Args>(args)...); } // Duplicate 1. // Const ref version template <> struct FooClass<Bar const&> { inline static void impl(const Bar& b) { std::cout << "dup1" << std::endl; } }; // Duplicate 2. // Copy version template <> struct FooClass<Bar> { inline static void impl(const

问题 I need help with my current workflow , though everthing works as expected but i would like to make the structure more robust. I have a application where i change the data by string literal. WAVEFRONT*TREEVIEW*Main$Text*GEOMETRY*TEXT SET TEXT ABCD as shown in the image where "Main$Text" is the path of the data item the the tree structure. 1) First step-> i have a class to handle the command string and take appropriate action. int SumCommandInterface::receiveCommand(std::string stdtsrCommand ,