Lecture 20-something CIS 208 Wednesday, April 27 th, 2005

Announcements Friday is last day of class Final homework is assigned Due in two weeks

Final Assignment Build an electronic address book. Use either C or C++ May work in pairs.

Final HW Due Wednesday of final’s week, by noon. Turn in source code and a manual or readme file. Tell me about the different features.

Object Orientated design Hiding implementation Let’s the user not care about how things work. Primary purpose of OO design.

OO Design Give objects most of the functionality Give the user as many choices as possible. Main programs should be simple.

References Call-by-reference without pointers Lets the user forget about pointers. Accessed without pointer notion. CBR only.

references. A swap function void swap(int *p1, int *p2) { int temp = *p1; *p1 = *p2; *p2 = temp; } int a = 1, b =2; swap(&a,&b);

Now easier void swap(int &p1, int &p2){ int temp = p1; p1 = p2; p2 = temp; } int a = 1, b= 2; swap(a,b); Don’t need to use * or & anymore Call by value is replaced with call by reference

Some issues Can’t change where reference is pointing. Passing object references doesn’t call deconstructor Can’t reference a reference Can’t create arrays of references Must be initialized.

Returning references char &replace(int i); //return a reference char s[80] = “Hello there”; int main() { replace(5) = ‘X’; cout << s; return 0; } char &replace(int i) { return s[i]; }

Independent references int main() { int a = 10; int &ref = a; ref = 100; cout << a << “ “<< ref; int b = 19; ref = b; cout <<a << “ “ << ref; ref--; cout << a << “ “ << ref; return 0; }

derived references base reference can point to derived object. Not the other way around.