Class template for numeric types

by

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.

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.

As of C++20, concepts make this much easier and don’t spoil the interface:

#include <concepts>

template<typename T>
concept arithmetic = std::integral<T> or std::floating_point<T>;

template<typename T>
  requires arithmetic<T>
struct S{};
// Shorthand: template<arithmetic T> struct S {};

Do note that there are many user types meant to be used arithmetically as well, though, so a more general concept that covers the operations you’re looking for instead of the types you’re looking for would be preferable in a generic interface.

More Related Contents:

  1. Optimization code for a debug function (c++11 with templates) [closed]
  2. C++11 does not deduce type when std::function or lambda functions are involved
  3. Why can’t the template argument be deduced when it is used as template parameter to another template?
  4. Can someone explain this template code that gives me the size of an array? [duplicate]
  5. Why can’t I use float value as a template parameter?
  6. Explicit specialization in non-namespace scope [duplicate]
  7. Accessing inherited variable from templated parent class [duplicate]
  8. SFINAE to check for inherited member functions
  9. Template Constraints C++
  10. When to use std::forward to forward arguments?
  11. Function signature-like expressions as C++ template arguments
  12. How to detect existence of a class using SFINAE?
  13. C++ template copy constructor on template class
  14. SFINAE works differently in cases of type and non-type template parameters
  15. Making a template parameter a friend?
  16. C++ static template member, one instance for each template type?
  17. Can the point-of-instantiation be delayed until the end of the translation unit?
  18. How to pass a template function in a template argument list
  19. How to make std::make_unique a friend of my class
  20. c++ automatic factory registration of derived types
  21. C++ Template Metaprogramming – Is it possible to output the generated code?
  22. Making a C++ class a Monitor (in the concurrent sense)
  23. Why the initializer of std::function has to be CopyConstructible?
  24. std::enable_if : parameter vs template parameter
  25. calculating factorial using template meta-programming
  26. Is there a way to write make_unique() in VS2012?
  27. Dependent scope and nested templates
  28. Can I use the result of a C++17 captureless lambda constexpr conversion operator as a function pointer template non-type argument?
  29. Check if a type is passed in variadic template parameter pack
  30. using extern template (C++11) to avoid instantiation

Leave a Comment