c++ - Class template for numeric types

Question

How do I write a class template that accepts only numeric types (int, double, float, etc.) as template?

question from:https://stackoverflow.com/questions/14294267/class-template-for-numeric-types

Answer 1

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
}

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.

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.