Question

Given the class below, which answer choice would be an implementation of the default constructor (without an initialization list)?

class MyInteger {
    private:
       int num;
    public:
       MyInteger();
       MyInteger(int newint);
       void setInt(int newint);
       int getInt();
       int operator[](int index);
};

  

MyInteger::MyInteger(int newNum) { num = newNum; }

   

MyInteger::MyInteger() { num = 0; }

   

MyInteger::MyInteger(int newNum = 0) { num = newNum; }

   

MyInteger::MyInteger(int newNum) : num{0} {;}

   

MyInteger::MyInteger(int newNum = 0) : num{0} {;}

   

MyInteger::MyInteger() : num{0} {;}

   

MyInteger::MyInteger(newNum) { num = newNum; }

Answer 1

Given MyInteger class definition:

class MyInteger {
    private:
       int num;
    public:
       MyInteger();
       MyInteger(int newint);
       void setInt(int newint);
       int getInt();
       int operator[](int index);
};

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The default constructor for the class MyInteger is
MyInteger::MyInteger()
{
   num = 0;
}

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Default constructor : A constructor contains the class name same as class name and it does not take any arguments or parameters and set the default values like 0 for integer,float and double and empty for string type variables.
Therefore, the correct option is
MyInteger::MyInteger()
{
   num = 0;
}