How to Determine if a Class is a Specialization of a Class Template in C ?

Identifying Template Specializations

In C , it is sometimes necessary to determine if a given class is a specialization of a particular class template. For instance, consider the following class template:

template <class T>
struct A {};

Say we have a type CompareT. How can we verify if it is an A<> for some type ? Consider the following example:

template<class CompareT>
void compare(){
   // is this A ?
   cout << is_same< A<*> , CompareT >::value;     // A<*> ????
}

int main(){
  compare< A<int> >();
}

In this example, we expect A to match A<*>, resulting in a print statement of 1.

Solution:

One approach to address this problem is to utilize template metaprogramming. Here's a snippet that allows you to specify the desired template to be matched against:

template <class T, template <class...> class Template>
struct is_specialization : std::false_type {};

template <template <class...> class Template, class... Args>
struct is_specialization<Template<Args...>, Template> : std::true_type {};

static_assert(is_specialization<std::vector<int>, std::vector>{}, "");
static_assert(!is_specialization<std::vector<int>, std::list>{}, "");

This solution provides a convenient way to check if a given type is indeed a specialization of a specific class template.

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