class-template

问题 I'm writing a class template like stl vector,and two constructors are like this: template<class T> vector<T>::vector(size_t count, const T&value) :bg(new T[count]), ed(bg + count), cap(ed) { for (auto it = bg; it != ed; ++it) *it = value; }//bg ed cap are all T* template<class T> template<class Input> vector<T>::vector(Input first, Input second) : bg(new T[second - first]), ed(bg + (second - first)), cap(ed) { memcpy(bg, (void*)first, sizeof(T)*(second - first)); } so if I do this vector<int

问题 I'm writing a class template like stl vector,and two constructors are like this: template<class T> vector<T>::vector(size_t count, const T&value) :bg(new T[count]), ed(bg + count), cap(ed) { for (auto it = bg; it != ed; ++it) *it = value; }//bg ed cap are all T* template<class T> template<class Input> vector<T>::vector(Input first, Input second) : bg(new T[second - first]), ed(bg + (second - first)), cap(ed) { memcpy(bg, (void*)first, sizeof(T)*(second - first)); } so if I do this vector<int

问题 I'm writing a class template like stl vector,and two constructors are like this: template<class T> vector<T>::vector(size_t count, const T&value) :bg(new T[count]), ed(bg + count), cap(ed) { for (auto it = bg; it != ed; ++it) *it = value; }//bg ed cap are all T* template<class T> template<class Input> vector<T>::vector(Input first, Input second) : bg(new T[second - first]), ed(bg + (second - first)), cap(ed) { memcpy(bg, (void*)first, sizeof(T)*(second - first)); } so if I do this vector<int

问题 Member functions of template classes can be fully specialized, e.g. template<class A> struct MyClass { // Lots of other members int foo(); }; template<class A> MyClass<A>::foo() { return 42; } template<> MyClass<int>::foo() { return 0; } would compile without problems. Note that foo() is not a template function so this is not about template function specialization (I can understand partial specialization is not allowed there as it would become incredibly confusing in combination with

来源： https://stackoverflow.com/questions/63896028/defining-a-single-template-for-a-member-function-within-a-class-template-with-bo

来源： https://stackoverflow.com/questions/63896028/defining-a-single-template-for-a-member-function-within-a-class-template-with-bo

来源： https://stackoverflow.com/questions/57563594/partial-class-template-argument-deduction-in-c17

问题 This question already has answers here : Why do I have to access template base class members through the this pointer? (3 answers) Closed 7 months ago . I have the following code which compiles successfully in c++14. template<class T, class ...Args> class B { public: using AbcData = int; }; template<typename ...Args> class D : public B<float, Args...> { public: AbcData m_abc; }; But when compiled in c++17, it gives the following error. error C2061: syntax error: identifier 'AbcData' What is

问题 This question already has answers here : Why do I have to access template base class members through the this pointer? (3 answers) Closed 7 months ago . I have the following code which compiles successfully in c++14. template<class T, class ...Args> class B { public: using AbcData = int; }; template<typename ...Args> class D : public B<float, Args...> { public: AbcData m_abc; }; But when compiled in c++17, it gives the following error. error C2061: syntax error: identifier 'AbcData' What is

问题 In C++17, this code is illegal: constexpr int foo(int i) { return std::integral_constant<int, i>::value; } That's because even if foo can be evaluated at compile-time, the compiler still needs to produce the instructions to execute it at runtime, thus making the template instantiation impossible. In C++20 we will have consteval functions, which are required to be evaluated at compile-time, so the runtime constraint should be removed. Does it mean this code will be legal? consteval int foo(int