英文:
Right syntax for a C++ non-type template template with a given type
问题
I have a class templated over a non-type attribute pointer over a template type, here a std::optional.
#include <optional>class A{public:std::optional<int> i;};template <typename C, typename T, std::optional<T> C::*optionalPtr>class OptionalHolder3{void doStuff(C &c);};using OH3 = OptionalHolder3<A, int, &A::i>;
It works well but I was curious if I could make it easier to use, by reducing the number of required template arguments, but I can't find the right syntax:
// Doesn't compiletemplate <typename C, template<class T> std::optional<T> C::*optionalPtr>class OptionalHolder2{};// Doesn't compiletemplate <template<class C, class T> std::optional<T> C::*optionalPtr>class OptionalHolder1{};using OH2 = OptionalHolder2<A, &A::i>;using OH2 = OptionalHolder1<&A::i>;
Is this possible and how do I do it?
英文:
I have a class templated over a non-type attribute pointer over a template type, here a std::optional.
#include <optional>class A{public:std::optional<int> i;};template <typename C, typename T, std::optional<T> C::*optionalPtr>class OptionalHolder3{void doStuff(C &c);};using OH3 = OptionalHolder3<A, int, &A::i>;
It works well but I was curious if I could make it easier to use, by reducing the number of required template arguments, but I can't find the right syntax:
// Doesn't compiletemplate <typename C, template<class T> std::optional<T> C::*optionalPtr>class OptionalHolder2{};// Doesn't compiletemplate <template<class C, class T> std::optional<T> C::*optionalPtr>class OptionalHolder1{};using OH2 = OptionalHolder2<A, &A::i>;using OH2 = OptionalHolder1<&A::i>;
Is this possible and how do I do it?
答案1
得分: 2
你可以使用 auto (C++17) 来实现这个：
template <auto>class OptionalHolder; // 无定义template<typename C, typename T, std::optional<T> C::*optionalPtr>class OptionalHolder<optionalPtr>{void doStuff(C &c);};
C++20 中的概念可能可以用来替代该特化，但需要一些特性来提取 T 和 C。
英文:
You might use auto (C++17) for that:
template <auto>class OptionalHolder; // No definitiontemplate<typename C, typename T, std::optional<T> C::*optionalPtr>class OptionalHolder<optionalPtr>{void doStuff(C &c);};
concepts from C++20 might be used instead of that specialization, but it would require some traits to extract T and C.
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论