数字类型的类模板 [英] Class template for numeric types
问题描述
如何编写仅接受数字类型( int
, double
, float
等)作为模板?
How do I write a class template that accepts only numeric types (int
, double
, float
, etc.) as template?
推荐答案
您可以使用 std :: is_arithmetic
类型特征。如果只想启用具有此类类型的类的实例化,请与 std :: enable_if
:
You can use the std::is_arithmetic
type trait. If you want to only enable instantiation of a class with such a type, use it in conjunction with std::enable_if
:
#include <type_traits>
template<
typename T, //real type
typename = typename std::enable_if<std::is_arithmetic<T>::value, T>::type
> struct S{};
int main() {
S<int> s; //compiles
S<char*> s; //doesn't compile
}
对于版本enable_if
更易于使用,并且免费添加了 disable_if
,我强烈建议阅读关于这件事的这篇精彩文章。
For a version of enable_if
that's easier to use, and a free addition of disable_if
, I highly recommend reading this wonderful article on the matter.
ps在C ++中,上述技术的名称称为替换失败不是错误(大多数使用缩写词SFINAE)。您可以在维基百科或 cppreference.com 。
p.s. In C++, the technique described above has a name called "Substitution Failure Is Not An Error" (most use the acronym SFINAE). You can read more about this C++ technique on wikipedia or cppreference.com.
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