Specializations

Morning!

Today, I want to show the specialize of classes. Thereby, you can give a diferent implementation.

Templates are so useful but sometimes could be necessary to make exceptions. C++ provide this tool that is similar to override functions.


Testing specialitzations:

#include <iostream>

//base case or primary template
template <typename T1, typename T2>
class Example{
     private:
         T1 _element1;
         T2 _element2;
     public:
         Example(){ 
             std::cout << "Example" << std::endl;
         }
};

//Specializations or also called partial or full specialization
//depending on each case

template <typename T>
class Example<T, T>{
     private:
         int _element1;
         int _element2;
     public:
         Example(){ 
             std::cout << "Example same class" << std::endl;
         }
};


template <typename T>
class Example<T, int>{
     private:
         int _element1;
         int _element2;
     public:
         Example(){ 
             std::cout << "Example template and int" << std::endl;
         }
};

template <typename T1,typename T2>
class Example<T1*,T2*>{
     private:
         int _element1;
         int _element2;
     public:
         Example(){ 
             std::cout << "Example template* and template* " << std::endl;
         }
};

int main(){
     Example<int,float> ex1;
     Example<float,float> ex2;
     Example<float,int> ex3;
     Example<int*,float*> ex4;
     //Example ex5; // error:
     /*
      * main.cpp:57:22: error: ambiguous class template instantiation for ‘class Example<int, int>’
      * main.cpp:19:20: error: candidates are: class Example<T, T>
      * main.cpp:31:22: error:                 class Example<T, int>
      * 
      * To fix it we might specify:
      * 
      * template <>
      * class Example<int,int>
      */
     
     //Example ex6; // error:
     /*
      * main.cpp:64:24: error: ambiguous class template instantiation for ‘class Example<int*, int*>’
      * main.cpp:19:20: error: candidates are: class Example<T, T>
      * main.cpp:42:23: error:                 class Example<T1*, T2*>
      * 
      * To solve this issue we could implement a specialitzacion for pointers
      * of the same type:
      * 
      * template<typename T>
      * Example<T*, T*>
      * 
      */
}