Function to explicitly istantiate a given template function with more standard types?

Question

I have the following question. Supposing I have a header file header.hpp with this template function declaration:

template <typename T> extern T func();

And in the header.cpp file I have the function definition:

template <typename T> T func() { \* do something */ };

//Following lines are for explicit istantiation of the template for some types:
template double func <double> (); //1
template int func <int>(); //2
//And others...

Does exists a function / class or something else which allows me to explicitly istantiate a template class definition for more templated types without the needing of writing something like lines 1 or 2 of the previous code everytime?

I am searching for something like, for example:

void function ( template_function list_of_types )
 {
  //explicit istantiations of the template_function for the types given in the list_of_types container...
 }

The signature doesn't have to be as the one above, but also similar, the important thing is that it works as I said before. Thanks.

Answer 1

You could use concepts (or requires) and create specialized versions of your template.

So if you have

void func(auto t) { ...}

you could define a concept "AllowedNumericalTypes" and write another template like

void func(AllowedNumericalTypes auto t) { /*1 and 2 */ }

The compiler will choose the most matching version of your func methods and then call those.

btw. template<typename T> void func(T t)
 is identical to 
void func(auto t)