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Default keyword in C++



class collar {
public:
collar() { std::cout <<  " collar is born.\n"; }  //Since collar in dog class invokes default constructor in collar
};

 class dog {
collar m_collar;
string& m_name;   // Reference should be initialized, hence leads to an error.
};

 int main() {
dog dog1;
}
output:
main.cc:13: error: no matching function for call to `dog::dog()'
main.cc:8: note: candidates are: dog::dog(const dog&)

// Add to dog:
// string& m_name; 
// Result: not compilable because age is not initialized.



/* C++ 11 Update: */
class dog {
   public:
      dog() = default;
      dog(string name) {...};
}

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