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/

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

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

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;
	};

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)
	{
	};

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;
	}

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));
	}

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);
	}

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 << "]"
	}

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

Breaking Abstraction

	// Somewhere inside Cons.cpp
	int Cons::peekX() {
	return p.x;
	}
	int Cons::peekY() {
	return p.y;
	}

Instance to Instance Access

	void Point::add(Point p) {
	p.x = p.x + this->x;
	p.y = p.y + this->y;
	}

That’s a Wrap

	Reading
		7.1 – 7.7