國立暨南國際大學 97 學年度第二學期小考試卷

(考試時間: 10:10-10:30)

1. (10%) Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).

   // Operator Overloading
   #include <iostream>
   using std::cout;
   using std::endl;
   
   class CComplex
   {
   public:
           double real;
           double imaginary;
   
           CComplex(double a = 0.0, double b = 0):
           real(a), imaginary(b)
           { }
   
           void Show()
           {
                   cout << real;
                   if (imaginary<0.0)
                           cout << imaginary << "i";
                   else if
                           (imaginary > 0.0)
                           cout << "+" << imaginary << "i";
                   cout  << "\n";
           }
   
           CComplex operator+(CComplex c)
           {
                   CComplex sum;
                   sum.real = this->real + c.real;
                   sum.imaginary = this->imaginary + c.imaginary;
                   return sum;
           }
   };
   
   int main()
   {
           CComplex c1(1,2);
           CComplex c2(3,0);
           CComplex c3 = c1 + c2;
           c1.Show();
           c2.Show();              // Hint: "cout << 3.0" will display "3".
           c3.Show();
   }
   
   
   
   
   
   
   
   
   
   

2.  (10%) Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is
   incorrect, point out the mistake(s).
   
   #include <iostream>
   #include <cstring>
   using std::cout;
   using std::endl;
   
   class CMessage
   {
     private:
       char* pmessage;                    // Pointer to object text string
   
     public:
       // Function to display a message
       void ShowIt() const
       { cout << endl << pmessage; }
   
       // Overloaded assignment operator for CMessage objects
       CMessage& operator=(const CMessage& aMess)
       {
         if(this == &aMess)               // Check addresses, if equal
           return *this;                  // return the 1st operand
   
         // Release memory for 1st operand
         delete[] pmessage;
         pmessage = new char[ strlen(aMess.pmessage) +1];
   
         // Copy 2nd operand string to 1st
         strcpy(this->pmessage, aMess.pmessage);
   
         // Return a reference to 1st operand
         return *this;
       }
   
       // Constructor definition
       CMessage(const char* text = "Default message")
       {
         pmessage = new char[ strlen(text) +1 ]; // Allocate space for text
         strcpy(pmessage, text);                 // Copy text to new memory
       }
   
       // Destructor to free memory allocated by new
       ~CMessage()
       {
         delete[] pmessage;               // Free memory assigned to pointer
       }
   };
   
   int main()
   {
     CMessage motto1("Brazil");
     CMessage motto2("India");
     CMessage motto3("Russia");
     CMessage motto4("Vietnam");
   
     motto3 = motto2 = motto1;                       // Use new assignment operator
   
     cout << "motto2 contains - ";
      motto2.ShowIt();
     cout << endl;
   
     (motto2 = motto3) = motto4;
   
     cout << "motto2 now contains - ";
     motto2.ShowIt();
     cout << endl;
   
     return 0;
   }