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Compiler Generated Default Constructor with default keyword in in c++ | C++ 11

Compiler Generated Default Constructor :
In C++ 3.0 :  Compiler results an error if there any other constructor and missing default constructor and you try to invoke default constructor.

class CAT {
   CAT(int age) {}
};

 CAT d1;  // Error: compiler will not generate the default constructor


// C++ 11:  With the default keyword, it forced the compiler to generate default constructor even if the is any other constructor.

class CAT {
   CAT(int age);
   CAT() = default;    // Force compiler to generate the default constructor
};
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