#include <iostream>
#include <type_traits>
 
struct base { };
struct derived : base { };
struct anotherbase { };
struct anotherderived : anotherbase { };
 
template<typename T, bool = std::is_base_of<base, T>::value
                         || std::is_base_of<anotherbase, T>::value>
struct Type { };
 
template<typename T>
struct Type<T, true>
{
   typedef float mytype;
};
 
int main()
{
   Type<base>::mytype a1 = 4.2f;
   Type<anotherderived>::mytype a2 = 8.4f;
   std::cout << a1 << '\n' << a2 << '\n';
}

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