CSE 2341 - Honors Principles of Computer Science I

1. CSE 2341 - HonorsPrinciples of Computer Science I Spring 2008 Mark Fontenot mfonten@engr.smu.edu Note Set 4

2. Quick Look Static vs. Local Variables Friendship Memberwise Assignment to copy two objects

3. Static Member • If a member is declared static • it is shared by all objects of the same class • it must be defined outside of the class • may be accessed before any instances are created

4. Example – with pictures class myCls { private: int x, y; public: myCls(){x = 5; y = 6;} }; int main() { myCls a; myCls b; return 0; } x 5 a y 6 x 5 b y 6

5. Example – with pictures class myCls { private: int x, y; static int p; public: myCls(){x = 5; y = 6;} }; int myCls::p = 10; int main() { myCls a; myCls b; return 0; } p 10 x 5 a y 6 x 5 b y 6

6. Example Class With Static Member #ifndef BUDGET_H #define BUDGET_H // Budget class declaration class Budget { private: static float CorpBudget; float DivBudget; public: Budget(void) { DivBudget = 0; } void AddBudget(float B) { DivBudget += B; CorpBudget += B; } budget.h

7. Example Class With Static Member float GetDivBudget(void) { return DivBudget; } float GetCorpBudget(void) { return CorpBudget; } }; //definition of static data member double Budget::CorpBudget = 0; #endif budget.h

8. Example Class With Static Member #include <iostream> #include <iomanip>using namespace std; #include "budget.h" // For Budget class int main() { Budget Divisions[4]; for (int Count = 0; Count < 4; Count++) { float Bud; cout << "Enter the budget request for “ << “division "; cout << (Count + 1) << ": "; cin >> Bud; Divisions[Count].AddBudget(Bud); } budgetDriver.cpp

9. Example Class With Static Member cout.precision(2); cout.setf(ios::showpoint | ios::fixed); cout << "\nHere are the division budget “ << “requests:\n"; for (Count = 0; Count < 4; Count++) { cout<<"\tDivision "<<(Count + 1)<<"\t$ "; cout << Divisions[Count].GetDivBudget(); cout << endl; } cout << "\tTotal Budget Requests:\t$ "; cout << Divisions[0].GetCorpBudget() << endl; return 0; } budgetDriver.cpp

10. Example Class With Static Member Enter the budget request for Division 1: 100000 Enter the budget request for Division 2: 200000 Enter the budget request for Division 3: 300000 Enter the budget request for Division 4: 400000 Here are the division budget requests: Division 1 $ 100000.00 Division 2 $ 200000.00 Division 3 $ 300000.00 Division 4 $ 400000.00 Total Budget Requests: $ 1000000.00

11. Static Member Functions static <return type><function name>(<parameter list>); callable before any objects are instantiated static member functions can access static data members before any objects are instantiated provides ability for specialized set-up routines in an object.

12. Example Class With Static Member #ifndef BUDGET_H #define BUDGET_H // Budget class declaration class Budget { private: static float CorpBudget; float DivBudget; public: Budget() { DivBudget = 0; } void AddBudget(float B) { DivBudget += B; CorpBudget += B; } budget2.h

13. Example Class With Static Member float GetDivBudget(void) { return DivBudget; } float GetCorpBudget(void) { return CorpBudget; } static void mainOffice(float); }; #endif budget2.h

14. Example Class With Static Member #include “budget2.h" // Definition of static member of Budget class float Budget::corpBudget = 0; //Definition of static member function MainOffice. //This function adds the main office's budget // request to the CorpBudget variable. void Budget::mainOffice(float moffice) { corpBudget += moffice; } budget2.cpp

15. Example Class With Static Member //Demonstrates static member function #include <iostream> #include <iomanip> #include "budget2.h"//For Budget class declarationusing namespace std; int main() { int count; float mainOfficeRequest; const int numDivisions = 4; cout << "Enter the main office's budget “ << “request: "; cin >> mainOfficeRequest; Budget Divisions[numDivisions]; Budget::mainOffice(mainOfficeRequest); budgetDriver2.cpp

16. Example Class With Static Member for (int Count = 0; Count < 4; Count++) { float budgetAmount; cout << "Enter the budget request for division "; cout << (count + 1) << ": "; cin >> budgetAmount; divisions[Count].addBudget(budgetAmount); } cout << setprecision(2); cout << showpoint << fixed; cout << "\nHere are the division budget requests:\n"; for (count = 0; count < 4; count++) { cout << "\tDivision " << (count + 1) << "\t$ "; cout << divisions[count].getDivisionBudget() << endl; } budgetDriver2.cpp

17. Example Class With Static Member cout << "\tTotal Requests (including main office):” << “ $ "; cout << divisions[0].getCorpBudget() << endl; return 0; } budgetDriver2.cpp Enter the main office's budget request: 100000 Enter the budget request for Division 1:100000 Enter the budget request for Division 2:200000 Enter the budget request for Division 3:300000 Enter the budget request for Division 4:400000 Here are the division budget requests: Division 1 $ 100000.00 Division 2 $ 200000.00 Division 3 $ 300000.00 Division 4 $ 400000.00 Total Requests (including main office): $ 1100000.00

18. Friends of Classes

19. friend <retType><function name>(<paramList>); • Friend Function • Not a member function of the class • has access to the private data members of the class

20. Friendship #ifndef AUXIL_H #define AUXIL_H class Budget;// Forward declaration of Budget class class AuxiliaryOffice { private: float auxBudget; public: AuxiliaryOffice() { auxBudget = 0; } void addBudget(float, Budget&); float getDivisionBudget() { return auxBudget; } }; #endif auxil.h

21. Friendship #include "auxil.h" #include "budget3.h" void AuxiliaryOffice::addBudget(float b, Budget&div) { auxBudget += b; div.corpBudget += b; } auxil.cpp

22. Example with Friendship #ifndef BUDGET3_H #define BUDGET3_H #include "auxil.h”//For Aux class declaration class Budget { private: static float corpBudget; float divisionBudget; public: Budget() { divisionBudget = 0; } void addBudget(float b) { divisionBudget += b; corpBudget += b; } budget3.h

23. Example with Friendship float getDivisionBudget(void) { return divisionBudget; } float getCorpBudget(void) { return corpBudget; } static void mainOffice(float); friend void AuxiliaryOffice::addBudget (float, Budget&); }; #endif budget3.h

24. Example with Friendship #include “budget3.h" // Definition of static member of Budget class float Budget::corpBudget = 0; //Definition of static member function MainOffice. //This function adds the main office's budget //request to the CorpBudget variable. void Budget::mainOffice(float moffice) { corpBudget += moffice; } budget3.cpp

25. Example with Friendship #include <iostream> #include <iomanip> #include "budget3.h" using namespace std; int main(int) { int count; float mainOfficeRequest; const int numDivisions = 4; cout << "Enter the main office's ” << budget request: "; cin >> mainOfficeRequest; Budget::mainOffice(mainOfficeRequest); Budget divisions[numDivisions]; AuxiliaryOffice auxOffices[numDivisions]; budgetDriver3.cpp

26. Example with Friendship for (count = 0; count < numDivisions; count++) { float budgetAmount; cout << "Enter the budget request for “ << “division "; cout << (count + 1) << ": "; cin >> budgetAmount; divisions[count].addBudget(budgetAmount); cout << "Enter the budget request for “ << “division "; cout << (count+1) << "'s\nauxiliary office: "; cin >> budgetAmount; auxOffices[count].addBudget(budgetAmount, divisions[Count]); } budgetDriver3.cpp

27. Example with Friendship cout << setprecision(2); cout << showpoint << fixed; cout << "Here are the division budget requests:\n"; for (count = 0; count < 4; count++) { cout << "\tDivision " << (count + 1) << "\t\t\t$ "; cout << setw(7); cout << divisions[count].getDivisionBudget() << endl; cout << "\tAuxiliary Office of Division " <<(count+1) << "\t$ "; cout << auxOffices[count].getDivisionBudget() << endl; } cout <<"Total Requests (including main office): $ "; cout << divisions[0].getCorpBudget() << endl; return 0; } budgetDriver3.cpp

28. Example with Friendship Enter the main office's budget request: 100000 Enter the budget request for Division 1: 100000 Enter the budget request for Division 1's auxiliary office: 50000 Enter the budget request for Division 2: 200000 Enter the budget request for Division 2's auxiliary office: 40000 Enter the budget request for Division 3: 300000 Enter the budget request for Division 3's auxiliary office: 70000 Enter the budget request for Division 4: 400000 Enter the budget request for Division 4's auxiliary office: 65000

29. Example with Friendship Here are the division budget requests: Division 1: $100000.00 Auxiliary office of Division 1: $50000.00 Division 2: $200000.00 Auxiliary office of Division 2: $40000.00 Division 3: $300000.00 Auxiliary office of Division 3: $70000.00 Division 4: $400000.00 Auxiliary office of Division 4: $65000.00 Total Requests (including main office): $ 1325000.00

30. Classes as Friends Possible to make entire classes friends of another class Budget could make Auxiliary a friend with:friend class AuxiliaryOffice; All member functions of AuxiliaryOffice would have access to all private data members of Budget (even those added in later development)

31. Memberwise Assignment

32. Memberwise Assignment • = operator • can be used to assign one objects instance to another object instance • can be used to initialize one object with another objects data • default: each member from one instance is copied to its counterpart in the other instance

33. Memberwise Assignment #include <iostream> class Rectangle { private: float width; float length; public: void setWidth(float w) { width = w; } void setLength (float l){ length = l; } float getWidth() { return width; } float getLength() { return length; } float GetArea() { return width * length; } };

34. Memberwise Assignment int main() { Rectangle Box1, Box2; Box1.setWidth(10); Box1.setLength(20); cout << "Before the assignment:\n"; cout << "Box 1's Width: " << Box1.getWidth()<< endl; cout << "Box 1's Length: " << Box1.getLength() << endl; cout << "Box 1's Area: " << Box1.getArea() << endl; Box2 = Box1; cout << "------------------------\n"; cout << "After the assignment:\n"; cout << "Box 2's Width: " << Box2.getWidth() << endl; cout << "Box 2's Length: " << Box2.getLength() << endl; cout << "Box 2's Area: " << Box2.getArea() << endl; } Box1: Box2: ? ? 10 20 Before:

35. Memberwise Assignment int main() { Rectangle Box1, Box2; Box1.setWidth(10); Box1.setLength(20); cout << "Before the assignment:\n"; cout << "Box 1's Width: " << Box1.getWidth()<< endl; cout << "Box 1's Length: " << Box1.getLength() << endl; cout << "Box 1's Area: " << Box1.getArea() << endl; Box2 = Box1; cout << "------------------------\n"; cout << "After the assignment:\n"; cout << "Box 2's Width: " << Box2.getWidth() << endl; cout << "Box 2's Length: " << Box2.getLength() << endl; cout << "Box 2's Area: " << Box2.getArea() << endl; } Box1: Box2: 10 20 10 20 After:

36. ?