这是对 C++20 概念的正确使用吗？

Question

我有一个简单的 Vec3<T> class，我想使用 C++20 概念（带有 -std=c++20 的 Clang 10.0.0）更新它。新版本看起来像这样：

template <typename T> concept Arithmetic = std::is_arithmetic_v<T>;
template <typename T> concept FloatingPoint = std::is_floating_point_v<T>;

template <Arithmetic T> struct Vec3 {
  T x, y, z;

  /* operator overloading, etc.. */
  
  void normalize() requires FloatingPoint<T>;
};

这是对 C++20 概念的正确使用吗？ core guideline T11 recommends using standard concepts as much as possible, but I couldn't find the ones I wanted in the list of C++ named requirements，也不在 <concepts> 头文件中。是不是我的概念太具体了，根本不应该是概念？

我的原始代码混合使用 static_assert 和 SFINAE 来获得最终结果。

Answer 1

我们已经有了浮点类型的概念，它是 std::floating_point. The absence of std::arithmetic seems to be an oversight and has already been noted, see N4844，第 50 页：

US 193. C++20 lacks a concept for arithmetic types. This omission is surprising, as this is a fairly common use case. For example, suppose I wish to write a function that squares a number. Pre C++20, I might write:
template <typename T>
auto square(T x) {return x * x;}
In C++20, it would seem natural to be able to write:
auto square(std::arithmetic auto x) {return x * x;}
However, such a standard library concept is missing! Instead, we must write the more verbose:
template <typename T> requires std::is_arithmetic_v<T>
auto square(T x) {return x * x;}
Proposed change:
template<class T>
concept arithmetic = is_arithmetic_v<T>;

但是 std::arithmetic 应该如何定义的问题并不像看起来那么容易。参见 . As Barry noted in the comment, that proposed change was rejected。

这是对 C++20 概念的正确使用吗？

Is this a proper use of C++20 concepts?

c++

c++-concepts

c++20