This is a CLOSED-BOOK-CLOSED-NOTES exam consisting of five (5) questions. Write your answer in the answer booklet provided. 1. OO concepts (5 points)

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1 COMP2012H Object Oriented Programming and Data Structures Spring Semester 2013 Midterm Exam Soution March 26, 2013, 10:30-11:50am in Room 3598 Instructor: Chi Keung Tang This is a CLOSED-OOK-CLOSED-NOTES exam consisting of five (5) questions. Write your answer in the answer booket provided. 1. OO concepts (5 points) (a) What is poymorphism in object-oriented programming? (b) Express in ess than 40 words how the foowing concepts are reated: dynamic binding, virtua functions, overriding, static binding, operator overoading, STL. 2. Tempate and operator overoading (10 points) You are given the foowing cass tempate specification and a main program where its sampe output is aso given. Your tasks are (a) impement the four member functions; use member initiaizer as much as possibe when defining constructors (b) overoad operator+ as a member function; operator<< and the prefix operator++ as non-member function; you can assume the types to be instantiated T1 and T2 are primitive types (one exampe is shown in the main program) but no friend function is aowed. You must not impement functions other than the above to make the main program run. You can define a member functions within cass tempate Tupe (which is probaby easier with ess syntax to bother), or outside of the cass tempate. cass Tupe Tupe (); Tupe (const T1& t1, const T2& t2); T1 get_ee1() const; T2 get_ee2() const; void set_ee(t1 v1, T2 v2); T1 ee1; T2 ee2; int main() Tupe<int,doube> t1 (2, 4.5); Tupe<int,doube> t2 (4, 3.8); 1

2 Tupe<int,doube> t3 = t1 + t2; cout << t3 << end; ++t3; cout << t3 << end; return 0; // output is // (6, 8.3) // (7, 9.3) 3. STL and iterators (5 points) Compete the foowing program using STL agorithms copy and sort and iterators. A tota of ony three statements is needed. #incude <stdib.h> #incude <vector.h> #incude <string> #incude <agorithm> #incude <iostream> using namespace std; typedef istream_iterator_char; // compete the decaration int main() vector<char> v; istream_iterator_char start (cin); istream_iterator_char end; back_insert_iterator<vector<char> > dest (v); // use st s copy to read characters from cin and copy them to v // use st s sort to sort v // use st s to copy the sorted v to cout, each character foowed by a space 4. Order of Construction and Destruction (5 points) What is the output of running the foowing program? #incude <iostream> using namespace std; cass ub ub() cout << "" << end; ub() cout << "" << end; cass Lamp ub bub; Lamp() cout << "" << end; ~Lamp() cout << "~" << end; 2

3 cass Room Room() cout << "R" << end; ~Room() cout << "~R" << end; Lamp ; cass Living_Room : pubic Room Living_Room() cout << "L" << end; ~Living_Room() cout << "~L" << end; ub *b; Lamp ; int main () static Lamp ; Room r; Living_Room r; return 0; 5. Abstract ase Cass and Inheritance (10 points) Code up the abstract base cass asepoint and the derived cass Figure2P so that the program beow compies and runs. A sampe run is aso incuded. Use member initiaizer whenever possibe and the highest eve of information hiding (i.e., must have no pubic data members). #incude <iostream> #incude <string> using namespace std; cass asepoint // your definitions here cass Figure1P : pubic asepoint int p1; Figure1P(int px, int py, int r):p1(r),asepoint(px, py) virtua void info() asepoint::info(); cout << "property 1: p=" << p1 << end; cass Square : pubic Figure1P Square(int px, int py, int r):figure1p(px, py, r) return "square"; 3

4 cass Circe : pubic Figure1P Circe(int px, int py, int r):figure1p(px, py, r) return "circe"; cass Figure2P : pubic Figure1P // your definitions here cass Rectange : pubic Figure2P Rectange(int px, int py, int w, int h):figure2p(px, py, w, h) return "rectange"; cass Ova : pubic Figure2P Ova(int px, int py, int w, int h):figure2p(px, py, w, h) return "ova"; int main(void) asepoint **objs = new asepoint*[5]; // aocate space for 5 asepoint pointers, // they may be used to store derived casses // creating objects objs[0] = new Circe(7, 6, 55); objs[1] = new Rectange(12, 54, 21, 14); objs[2] = new Square(19, 32, 10); objs[3] = new Ova(43, 10, 4, 3); objs[4] = new Square(3, 41, 3); boo fag=fase; do cout << end << "" << end; cout << " " << end; cout << " " << end; char onum; cin >> onum; fag = ((onum >= 0 )&&(onum <= 4 )); if (fag) objs[onum- 0 ]->info(); whie(fag); // freeing memory for(int i=0;i<5;i++) deete objs[i]; deete [] objs; Sampe run 4

5 0 figure: circe position: x=7, y=6 property 1: p=55 1 figure: rectange position: x=12, y=54 property 1: p=21 property 2: p=14 2 figure: square position: x=19, y=32 property 1: p=10 3 figure: ova position: x=43, y=10 property 1: p=4 property 2: p=3 4 figure: square position: x=3, y=41 property 1: p=3 5 5

6 SOLUTIONS TO MIDTERM 1. OO concepts (5 points) (a) Working with objects without knowing their precise type; at compie or run time. (b) Dynamic binding is necessary for dynamic poymorphism, which is impemented in C++ using virtua functions in inheritance to get overriding done. Static binding achieves static poymorphism: STL and operator overoading are exampes in C++. (34 words) 2. Tempate and operator overoading (10 points) cass Tupe Tupe () : ee1(0), ee2(0) Tupe (const T1& t1, const T2& t2): ee1(t1), ee2(t2) Tupe operator+ (const Tupe& t) const return Tupe (ee1 + t.ee1, ee2 + t.ee2); T1 get_ee1() const return ee1; T2 get_ee2() const return ee2; void set_ee(t1 v1, T2 v2) ee1 = v1; ee2 = v2; T1 ee1; T2 ee2; /* // if defined outside of the cass Tupe<T1,T2> Tupe<T1,T2>::operator+ (const Tupe<T1,T2> &t) const return Tupe<T1,T2> (ee1 + t.ee1, ee2 + t.ee2); */ ostream& operator<< (ostream& os, const Tupe<T1,T2> &t) os << "(" << t.get_ee1() << ", " << t.get_ee2() << ")" ; return os; Tupe<T1,T2> operator++ (Tupe<T1,T2> &t) t.set_ee (t.get_ee1()+1, t.get_ee2()+1); return t; 6

7 3. STL and iterators (5 points) // use st s copy to read characters from cin and copy them to v copy (start, end, dest); // use st s sort to sort v sort(v.begin(), v.end()); // use st s to copy the sorted v to cout, each character foowed by a space copy (v.begin(), v.end(), ostream_iterator<char> (cout, " ")); 4. Order of Construction and Destructio (5 points) R ~R ~ R L ~L ~ ~R ~ ~ 5. Abstract ase Cass and Inheritance (10 points) cass asepoint int x, y; //position asepoint(int px, int py):x(px),y(py) virtua string type() = 0; virtua void info() cout << end << "figure: " << type() << end; cout << "position: x=" << x << ", y=" << y << end; cass Figure2P : pubic Figure1P int p2; Figure2P(int px, int py, int w, int h):p2(h),figure1p(px, py, w) virtua void info() Figure1P::info(); cout << "property 2: p=" << p2 << end; 7