Selecting a type in compile-time

As we discussed in the preceding topic, type is a basic part of a template. However, we can select a certain type based on the input from the user. Let's create a template that can decide what type should be used in the variable. The following types.cpp code will show the implementation of the template:

    /* types.cpp */
    #include <iostream>

    using namespace std;

    // Defining a data type
    // in template
    template<typename T>
    struct datatype
    {
      using type = T;
    };

    auto main() -> int
    {
      cout << "[types.cpp]" << endl;

      // Selecting a data type in compile time
      using t = typename datatype<int>::type;

      // Using the selected data type
      t myVar = 123;

      // Displaying the selected data type
      cout << "myVar = " << myVar;

      return 0;
    }

As we can see in the preceding code, we have a template named datatype. This template can be used to...