國立暨南國際大學 111 學年度第二學期小考試卷

1. (10%) Determine whether the syntax of the following code is correct or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   /* Return a value vs. Return a reference */
   #include <iostream>
   using std::ostream;
   
   class CInt {
   friend ostream& operator<<(ostream& output, const CInt& b);
   public:
       CInt(int n=0): value(n) {}
       CInt Inc() { ++value; return *this; }
   private:
       int value;
   };
   
   ostream& operator<<(ostream& output, const CInt& b) {
       output << b.value;
       return output;
   }
   
   int main()
   {
       int a = 0;
       CInt b(0);
       /* Function Chaining
          - https://cplusplus.com/forum/general/143639/ */
       std::cout << ++++a << ' ' << b.Inc().Inc() << std::endl;
       std::cout << a     << ' ' << b             << std::endl;
       return 0;
   }
   
   
2. (10%) Determine whether the syntax of the following code is correct or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   /* c_str() */
   #include <iostream>
   #include <string>
   
   int main()
   {
       std::string city("King");
       char ptr1[5] = { 0 };
       city.copy(ptr1, city.length());
       const char* ptr2 = city.c_str();
       city = "Land";
       std::cout << city << std::endl;
       std::cout << ptr1 << std::endl;
       std::cout << ptr2 << std::endl;
       return 0;
   }
   
   
   
3. (10%) Determine whether the syntax of the following code is correct or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   /* I/O Stream, File Stream, String Stream */
   #include <iostream>
   #include <fstream>
   #include <sstream>
   #include <string>
   #define N       5
   
   int main()
   {
       std::ofstream outfile("a.txt");
       for (int i=1; i<=N; ++i)
           for (int j=1; j<=i; ++j)
               outfile << j << (j==i?'\n':' ');
       outfile.close();
   
       int n;
       std::string line;
       std::ifstream infile("a.txt");
       while (getline(infile, line)) {
           std::cout << line.length() << '\t';
           int sum = 0;
           std::istringstream iss(line);
           while (iss >> n)
               sum += n;
           std::cout << sum << std::endl;
       }
       infile.close();
       return 0;
   }