何时使用`static_assert`而不是SFINAE？ [英] When to use `static_assert` instead of SFINAE?

问题描述

我一直在使用（并看到使用） static_assert 来标记不需要的模板参数值。但是，对于所有情况下，我发现它似乎更好，更优雅通过SFINAE禁用这些不需要的值。例如

 模板< typename T，
 class = std :: enable_if< std :: is_floating_point< T> ;: ：value> :: type> 
 struct Foo {...}; 
  

而不是

  template< typename T> 
 struct Foo {
 static_assert（std :: is_floating_point< T> :: value，
Foo< T> ;: T必须是浮点数:-(）; 
。所以我的问题：何时使用; 
}; 
  



<

p>我认为到目前为止我所学到的是以下

1 SFINAE是一个多功能和强大但可能非常复杂的工具，

2 SFINAE可用于多个任务，包括函数重载解析（其中一些似乎被视为其唯一目的）。一种相对简单的方法，除非它出现在（类或函数）的声明中，而不是其定义，所以 static_assert （或者可以在例如类转发声明中插入 static_assert ），这使得更多的逐字，因此更清晰的代码。但是，因为SFINAE是复杂的，它往往比一个简单的 static_assert 更难得到。

3 另一方面， static_assert 有一个更清晰的编译器错误消息的好处，有人似乎认为这是一个主要目的。

解决方案

我认为 static_assert 是正确的选择，如果你想强制执行 T 是一种浮点类型。此方法比SFINAE解决方案更清楚地说明您的意图。

I have been using (and seen used) static_assert to flag undesired values of template parameter values. However, for all cases I came across it seems better and more elegant to disable those undesired values via SFINAE. For example

template<typename T,
         class = std::enable_if<std::is_floating_point<T>::value>::type>
struct Foo { ... };

instead of

template<typename T>
struct Foo {
  static_assert(std::is_floating_point<T>::value,
                "Foo<T>: T must be floating point :-(");
  ...
};

So my question: when to use static_assert instead of SFINAE and why?

EDIT

I think what I've learned so far is the following

1 SFINAE is a versatile and powerful but potentially very complicated tool that can be used for many tasks, including function overload resolution (which some seem to regard as its only purpose).

2 SFINAE can be used in a relatively simple way where ever static_assert can, except that it appears in the declaration (of a class or function) rather than its definition (or is is possible to insert a static_assert into, say, a class forward declaration?). That makes more verbatim and hence clearer code. However, because SFINAE is complicated, it tends to be harder to get right than a simple static_assert.

3 On the other hand static_assert has the benefit of a clearer compiler error message, which some seem to regard as the main purpose of either.

解决方案

I think static_assert is the right choice if you want to enforce that T is a floating point type. This method states your intent more clearly than the SFINAE solution.

这篇关于何时使用`static_assert`而不是SFINAE？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！