CSE2050 Fall 2004 Final Exam, open book, open notes.  Name _________________

1. What does the following print? (2 pts each)

                                      ANSWERS
  char a[]="mouse";  cout << a+2;     use
  cout << *(a+2);                     u
  cout << char(*a+2);                 o      ('m'+2)
  cout << &a[2]-a;                    2
  (*a)--; cout << a;                  louse

2. Write a templated function that will print the elements of a vector,
list, or deque (assuming printable elements) using the normal << notation.
Elements should be separated by spaces.  For example: (30 pts)

  char *s = "abc";
  list<char> l(s, s+3);
  vector<int> v(l.begin(), l.end());  // ASCII codes of a, b, c
  deque<double> d(v.begin(), v.end());
  cout << l << v << d;  // a b c 97 98 99 97.0000 98.0000 99.0000

  // ANSWER
  template <class T>
  ostream& operator << (ostream& out, const T& x) {
    for (typename T::const_iterator p=x.begin(); p!=x.end(); ++p)
      out << *p << ' ';  // cannot use x[i] on a list
    return out;
  }


3. Class D lacks some of the methods required by the rule of 3.  Write
the base class B so that the compiler will disallow attempts to use
these faulty operations in D.  Make B abstract. (30 pts)

  class D: public B {
    int *p;
  public:
    D(int i): p(new int[i]) {}
    int& get(int i) {return p[i];}
    ~D() {delete[] p;}
  };

  // ANSWER
  class B {
  public:
    virtual int& get(int i) = 0;  // pure virtual
    virtual ~B() {}  // NOT pure
  protected:
    B() {}  // optional if there is at least one pure virtual function
  private:
    // The default copy constructor and assignment operator for D will
    // call the corresponding operations on B.  If they are private in B,
    // then an attempt to use them on a D will cause a compiler error.
    B(const B&);  // NOT virtual, implementation is optional
    B& operator=(const B&);  // NOT virtual, implementation is optional
  };


4. Write a program that takes real numbers as arguments and prints
the number of arguments, not counting duplicates.  (Hint, use a map).
For example: (30 pts)

  count 5.2 4.99 5.2 -8 -8.0
  3

  // ANWWER
  #include <iostream>
  #include <map>
  #include <cstdlib>  // for atof()
  using namespace std;
  int main(int argc, char** argv) {
    map<double, bool> m;  // or map<double, int>
    for (int i=1; i<argc; ++i)  // NOT i=0
      m[atof(argv[i])] = true;  // or ++m[...]
    cout << m.size() << endl;
    return 0;
  }