1. CSS 342 Data Structures, Algorithms, and Discrete Mathematics I
Lecture
Carrano CH1, C++ Interlude , C++ Interlude 5
C++ Book

2. Agenda Program 1 Discussion Deck of Cards: Class Design Encapsulation
Flush out card deck examples
friends
Constructors
Call by Reference
Overloading Operators: Rational Class

3. Program 1 Can I get away with a single constructor?
Where should I place const definitions?
What do I need to turn in?

4. Class Design Simple Complete Cohesive Descriptive Intuitive Minimal
No Public Data
Amenable to loosely couple

5. Problem 2
Design an interface for a class representing a deck of playing cards

6. #include "Card.h"
#include "Hand.h"
const int CARDS_IN_DECK = 52;
class Deck {
public:
Deck();
~Deck();
Card DealSingleCard();
Hand DealHand(int number);
void Shuffle();
void Cut();
int CountCardsRemaining();
void ReturnHand(Hand theHand);
void ReturnCard(Card theCard);
int CountValuesRemaining(int val);
int CountSuitsRemaing(Suit suit);
bool isEmpty();
bool isComplete();
private:
Card deck[CARDS_IN_DECK]; };

7. Interface Design Checklist
Constructors
Setters/Getters
Actions (verbs)
Operator Overloads
Private Data Types

8. Why C++ Object Oriented Programming (OOP)?
Abstraction <- Last Time
Encapsulation <- This Time
Hierarchy
Polymorphism

9. Encapsulation

10. Encapsulation and Information Hiding
Wall: Not only encapsulate the entire implementation but also make it invisible/inaccessible.
Slit: Interface of the implementation such as arguments and a return value.
Implementation
of method S
Program
that uses
method S
Function call with arguments
Return a value

11. Class
Classes: a new data type formed of a collection of data and a set of operations on the data
Data Structures: a construct within a programming language that stores a collection of data
Behave as a new data type
add
remove
query
Examples:
student lists
rational numbers
complex numbers
currency (cents/dollars)
length measurement (inches/feet)
weight measurement (oz/lbs)
Program
that uses
a class

12. Encapsulation at ground level
Program consists of
Driver file (main) – keep this quite small
Classes (ex, MyClass)
MyClass.h -- interface
MyClass.cpp -- implementation
Interface (.h file)
public: functions called by others
private: data, helper functions
Implementation (.cpp file)
MyClass::function()

13. Examples of private data Flush out deck example
const int CARDS_IN_DECK = 52;
class Deck {
public:
Deck();
Card DealSingleCard();
Hand DealHand(int number);
….interface as defined last time….
~Deck();
private:
Card deck[52]; };
enum Suit { Heart, Diamond, Club, Spade };
class Card {
public:
Card();
Card(int val, Suit suit);
~Card();
private:
int value;
Suit suit; };

14. Friends Declared on either functions or classes
Identified with the friend keyword
Non-member functions can access private data of an object if it has been declared a friend
Friendship is not transitive (my friend’s friend is not my friend)
Violates encapsulation
class Foo {
friend class TheClassToGrantAccess;
public:
private: }

15. Constructor Uses same name as class is constructs
Nothing returned; not even void
Default constructor created
Function executed on creation of object
Arrays: constructors called in increasing order Arr[0], Arr[1], Arr[2],…
Signature chooses constructor
Casting of call parameters done using normal casting rules
What’s in a constructor?
Normally used initialize private data as built-in types in C++ are undefined (int a; a is unknown state)
Generally side-effecting is not done

16. Add constructor(s) to Card
How about GETTERS/SETTERS?

17. CONST keyword usages Global definition of value which does not change
const int NUM_CARDS_IN_DECK = 52
(can also be done with preprocess #define but do not use)
Modifier on member function which does not change data in object
void MyFuntion(int p) const;
const reference to save space on passing in variable
void MyFunction(const MyParamType &mpt);
There are other usages but the above are the most common/useful

18. Computer Scientist of the Week
Presper Eckert
Chief Engineer first general purpose electronic digital computer (ENIAC)
Vaccuum tubes
Calculated ballistic tables for artillery
Presented first course in computers (Moore School Lectures)
Founded first commercial computer company
Designed first commercial computer, UNIVAC
Designed Von Neumann Architecture

19. C++ Fundamentals
LET’S CODE

20. string http://www.cprogramming.com/tutorial/string.html
Mutable; Copied not shared.
string firstName = "jimmy";
string lastName("hoffa");
string fullName;
fullName = firstName + " " + lastName;
cout << fullName << endl;
cout << "First and last letters are:" << fullName[0] << " " << fullName[fullName.length() - 1] << endl;
if (fullName == "jimmy hoffa") {
cout << "Found !!!! "; }
else
cout << "oh where oh where have you gone";

21. Call by Value, Reference, and Constant Reference
struct Rectangle {
int length;
int width; };
int Area(Rectangle rect)
int Area(Rectangle &rect)
int Area(const Rectangle &rect) {
int temp;
temp = rect.length;
rect.length = 35;
return(temp * rect.width); }
int main() {
int result;
Rectangle r = { 3, 3 };
result = Area(r);
cout << "length = " << r.length << endl;
cout << "width = " << r.width << endl;
cout << "Area = " << result << endl;
return 0; }

22. Class Bell

23. In class code
Write a function which takes two integers and “swaps” them

24. Call by Value, Reference, and Constant Reference
Arrays, Pointers, and Structures
Call by Value, Reference, and Constant Reference
Which of swap functions is appropriate?
void swap(string a, string b) {
string tmp = a;
a = b;
b = tmp; }
void swap(string &a, string &b) {
string tmp = a;
a = b;
b = tmp; }
void swap(const string &a, const string &b) {
string tmp = a;
a = b;
b = tmp; }
Which of findMax functions is appropriate?
int findMax(vector<int> a) {
int max = a[0];
int i;
for (i=1; i < a.size(); i++)
if (a[i] > max)
max = a[i];
return max; }
int findMax(vector<int> &a) {
int max = a[0];
int i;
for (i=1; i < a.size(); i++)
if (a[i] > max)
max = a[i];
return max; }
int findMax(const vector<int> &a) {
int max = a[0];
int i;
for (i=1; i < a.size(); i++)
if (a[i] > max)
max = a[i];
return max; }
CSS342: Introduction

25. Rational Class
Create a class to represent a rational number

26. Rational Class Create a class to represent a rational number
This should allow for
multiplication, division, addition, subtraction.
Comparison (eg, ==, !=)
Printing out to stream

27. Interface Design Checklist
Constructors
Setters/Getters
Actions (verbs)
Operator Overloads
Private Data Types

28. Rational.h: w/o Operating Overloads
#include <iostream>
#include <algorithm>
using namespace std;
class Rational {
public:
Rational();
Rational(int num, int den);
~Rational();
int getNumerator() const;
int getDemnominator() const;
bool setValue(int num, int den);
Rational Multiply(const Rational &rat) const;
Rational Divide(const Rational &rat) const;
Rational Subtract(const Rational &rat) const;
Rational Add(const Rational &rat) const;
void PrintRational(ostream &theStream) const;
private:
int numerator;
int denominator;
void reduce(); };

29. Rational.cpp: w/o Operator Overloading
Rational::Rational() {
numerator = 0;
denominator = 1; }
Rational::Rational(int num, int den)
numerator = num;
denominator = den;
reduce();
int Rational::getNumerator() const
return numerator;
int Rational::getDemnominator() const
return denominator;
bool Rational::setValue(int num, int den) {
if (den == 0)
return false; }
numerator = num;
denominator = den;
reduce();
return true;

30. Rational.cpp: w/o Operator Overloading
void Rational::reduce() {
int gcd = 1;
int minimum = min(numerator, denominator);
for (int i = 2; i <= minimum; i++)
if (((numerator % i) == 0) && ((denominator % i) == 0))
gcd = i; }
if (gcd > 1)
numerator /= gcd;
denominator /= gcd;
Rational Rational::Multiply(const Rational &rat) const {
Rational temp;
temp.numerator = numerator * rat.numerator;
temp.denominator = denominator * rat.denominator;
temp.reduce();
return temp; }
Rational Rational::Add(const Rational &rat) const {
Rational temp;
temp.numerator = (numerator * rat.denominator) + (rat.numerator * denominator);
temp.denominator = denominator * rat.denominator;
temp.reduce();
return temp; }

31. Operator Overload
Allowing for operators to work on classes in intuitive ways.
Key Examples:
Arithmetic: +, -, *, /
Comparison: ==, !=, <, >, <=, >=
Input: <<, >>
General rules for overloading
Whenever the meaning of an operator is not obviously clear and undisputed, it should not be overloaded
Always stick to the operator’s well-known semantics
Always provide all out of a set of related operations
Operators retain their precedence order

32. Overloading +,-,*,/ as member functions
class Rational {
public:
// Op Overloads
Rational operator*(const Rational &rat) const;
Rational operator/(const Rational &rat) const;
Rational operator-(const Rational &rat) const;
Rational operator+(const Rational &rat) const; };

33. Overloading input/output <<, >>
class Rational {
public:
friend ostream& operator<<(ostream &outStream, const Rational &rat);
friend istream& operator>>(istream &inStream, Rational &rat);
// Op Overloads
Rational operator*(const Rational &rat) const;
Rational operator/(const Rational &rat) const;
Rational operator-(const Rational &rat) const;
Rational operator+(const Rational &rat) const;

34. Overloading ==, !=, +=, etc…
class Rational {
friend ostream& operator<<(ostream &outStream, const Rational &rat);
friend istream& operator>>(istream &inStream, Rational &rat);
public:
// Op Overloads
Rational operator*(const Rational &rat) const;
Rational& operator*=(const Rational &rat);
Rational operator/(const Rational &rat) const;
Rational& operator/=(const Rational &rat);
Rational operator-(const Rational &rat) const;
Rational& operator-=(const Rational &rat);
Rational operator+(const Rational &rat) const;
Rational& operator+=(const Rational &rat);
bool operator==(const Rational &rat) const;
bool operator!=(const Rational &rat) const;

35. But wait…
Given we overloaded +, is there a better way to implement +=?
Actually, one should implement += first, and then used it to implement +
Same for -=/-, *=/*, and / /=

36. Using += overload to implement +
MyClass & MyClass::operator+=(const MyClass &rhs) {
... // Do the compound assignment work.
return *this; }
MyClass MyClass::operator+(const MyClass &other) const
MyClass result = *this;
result += other;
return result;

37. Resources on overloading.
-- rational class