1	CS 211: Introduction to Computer Programming II Instructor: Brian M. Dennis Teaching Assistants: Tom Lechner, Bin Lin, Rachel Goldsborough http://www.cs.northwestern.edu/~bmd/cs211/
2	A Previous Edition #ifndef _CONS_H_ #define _CONS_H_ 1 #include "Point.h" class Cons { public: Cons(Point* pi, Cons tail = 0); Cons(int xi, int yi, Cons tail = 0); Cons(); Point* car(); Cons* cdr(); ~Cons(); private: Point* p; Cons* tail; }; #endif
3	A Slightly New Edition #ifndef _CONS_H_ #define _CONS_H_ 1 #include "Point.h" class Cons { public: Cons(Point pi, Cons tail = 0); Cons(int xi, int yi, Cons tail = 0); Cons(); Point car(); Cons* cdr(); ~Cons(); private: Point p; Cons* tail; }; #endif
4	A Previous Edition #include <cstring> #include "Cons.h" #include <iostream> using namespace std; Cons::Cons(Point* pi, Cons tail) { p = pi; } Cons::Cons(int x, int y, Cons t) { p = new Point(x, y); tail = t; };
5	A Slightly New Edition #include <cstring> #include "Cons.h" #include <iostream> using namespace std; Cons::Cons(Point pi, Cons tail) : p(pi) { t = tail; } Cons::Cons(int x, int y, Cons t) : tail(t), p(x, y) { };
6	Overloaded Functions int max(int x, int y) { return (x <= y) ? y : x; } char* max(char* s1, char* s2) { return (strcmp(s1,s2) < 0) ? s2 : s1; } Point max(Point p1, Point p2) { int d1 = sqrt(p1.x() * p1.x() + p1.y() * p1.y()); int d2 = sqrt(p2.x() * p2.x() + p2.y() * p2.y()); return (d1 <= d2) ? p2 : p1; }
7	Overloaded Functions int max(int x, int y); float max(int x, int y); int max(float x, float y); char* max(char* s1, char* s2); Point max(Point p1, Point p2); int main(int argc, char* argv[]) { float f = max(100, 11); int i = max(1.1, 3.14159); max("Panthers", "Patriots"); max(Point(5,5), Point(0,4)); }
8	Overloaded Functions void print(ostream& os, char* s); void print(ostream& os, Point& p); void print(ostream& os, int i) int main(int argc, char* argv[]) { … print(cout, "It's Howdy Doody Time"); print(cout, Point(10, 20)) print(cout, 100) … exit(0); }
9	Overloaded Functions void print(ostream& os, Point p) { os << "[" << p.getX() << "," << p.gety() << "]"; } // What if we're really lazy and want void print(ostream& os, Point p) { os << "[" << p.x << "," << p.y << "]" }
10	Breaking Abstraction #ifndef _CONS_H_ #define _CONS_H_ 1 #include "Point.h" #include <iostream> using std::ostream; class Cons { public: Cons(Point pi, Cons tail = 0); Cons(int xi, int yi, Cons tail = 0); Cons(); Point car(); Cons* cdr(); ~Cons(); friend void print(ostream& os, Point p); friend class Cons; private: Point p; Cons* tail; }; #endif
11	Breaking Abstraction // Somewhere inside Cons.cpp int Cons::peekX() { return p.x; } int Cons::peekY() { return p.y; }
12	Instance to Instance Access void Point::add(Point p) { p.x = p.x + this->x; p.y = p.y + this->y; }
13	That’s a Wrap Reading 7.1 – 7.7