// crtpEquality.cpp
#include <iostream>
#include <string>
template<class Derived>
class Equality{};
template <class Derived>
bool operator == (Equality<Derived> const& op1, Equality<Derived> const & op2){
  Derived const& d1 = static_cast<Derived const&>(op1);     
  Derived const& d2 = static_cast<Derived const&>(op2); 
  return !(d1 < d2) && !(d2 < d1);
}
template <class Derived>
bool operator != (Equality<Derived> const& op1, Equality<Derived> const & op2){
  Derived const& d1 = static_cast<Derived const&>(op1);     
  Derived const& d2 = static_cast<Derived const&>(op2); 
  return !(d1 == d2);
}
struct Apple:public Equality<Apple>{
  Apple(int s): size{s}{};
  int size;
};
bool operator < (Apple const& a1, Apple const& a2){
  return a1.size < a2.size;
}
struct Man:public Equality<Man>{
  Man(const std::string& n): name{n}{}
  std::string name;
};
bool operator < (Man const& m1, Man const& m2){
  return m1.name < m2.name;
}
int main(){
  
  std::cout << std::boolalpha << std::endl;
  
  Apple apple1{5};
  Apple apple2{10}; 
  std::cout << "apple1 == apple2: " << (apple1 == apple2) << std::endl;
    
  Man man1{"grimm"};
  Man man2{"jaud"};
  std::cout << "man1 != man2: " << (man1 != man2) << std::endl;
  
  std::cout << std::endl;
    
}