Intro to Abstract Data Types

7/29/2019 Intro to Abstract Data Types

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IntroductiontoAbstractDataType&C++

NorBahiahHjAhmad&Dayang

NorhayatiA.

Jawawi

SCJ2013DataStructure&Algorithms

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ObjectivesAttheendoftheclassstudentsareexpectedto:

UnderstandAbstractDataTypeconcept ReviewC++programming

Declaring

aclass,

data

member

and

function

member

Creatingconstructoranddestructor

Pass objectasfunctionparameter

Returnobjectfromafunction

Arrayof

class

Pointertoclass

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Abstraction

Abstractdatatype(ADT)

x Acollectionofdataandasetofoperationsonthedata

x Giventheoperationsspecifications,theADTsoperations

canbeusedwithoutknowingtheirimplementationsor

howdata

is

stored,

Abstraction

Thepurposeofamoduleisseparated fromits

implementation Specificationsforeachmodulearewrittenbefore

implementation

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Abstraction

Dataabstraction

x Focuseson

the

operations of

data

(whatyou

can

do

to

a

collectionofdata),notontheimplementationofthe

operations(howyoudoit)

x

develop

each

data

structure

independently

from

the

rest

ofthesolution

Functionalabstraction

Separatesthepurposeofamodulefromits

implementation

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InformationHiding

Informationhiding

Hidethe

details

within

amodule.

Tolimitthewaytodealwithmoduleanddata,sothatothermodulecannotmodifythedata.

Makesthese

details

inaccessible

from

outside

the

module.

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AbstractionExample

6

bookbook

book

title

year

author

publisher

price

getData()

print()

checkPrice()

checkPublisher()

Abstracion of bookAbstracion of book

abstract to attributes

behavior

Abstraction of a book


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Encapsulation

Theprocessofcombiningdataandfunctionsintoa

singleunitcalledclass.

Theprogrammercannotdirectlyaccessthedata.

Dataisonlyaccessiblethroughthefunctionspresent

insidetheclass.

Dataencapsulationisanimportantconceptofdata

hiding.

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C++Classes

Aclassdefinesanewdatatype

Aclass

contains

data

members

and

methods

(memberfunctions)

Bydefault,

all

members

in

aclass

are

private

Butcanbespecifiedaspublic

Anobjectisaninstanceofaclass

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C++Class

Definition

9

class clasName{

public:list of data member declaration;list of function member declaration;

private:list of data member declaration;list of function member declaration;

}; // end class definition

public :membersthatareaccessiblebyothermodules

private :members

that

are

hidden

from

other

modules

and

canonlybeaccessedbyfunctionmemberofthesameclass.

class memberdeclarations:data memberand

functionmember


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ClassDefinition

for

Book

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classbook

{private:

// data member declaration as private

float price;

int year;

char author[20], title[25];

public:

book(); // Default constructor

// Constructor with parmeter

book(char *bkTitle,double bkPrice);

book(int = 2000);

// C++ function

void getData();void print( );

float checkPrice( )const;

char * getAuthor();

~book() ; // destructor

}; // end book declaration


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ClassMethods

Classmethodsconsistsof

Constructor

Destructor

C++functions.

const function

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Constructors Constructors

Usedto

create

and

initialize

new

instances

of

aclass

Isinvokedwhenaninstanceofaclassisdeclared

Havethesamenameastheclass

Haveno

return

type,

not

even

void

Aclasscanhaveseveralconstructors However,compilerwillgenerateadefaultconstructorifno

constructoris

defined.

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ConstructorProperties

Morethanoneconstructorcanbedeclared

Eachconstructor

must

be

distinguished

by

the

arguments.book();

book(char *bkTitle,double bkPrice);book(int = 2000);

Defaultconstructor: book();

Canhave

argument:

book(char *bkTitle,double bkPrice);

Canhavedefaultargument:

book(int = 2000); 13


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DefaultConstructor

Implementation

Setsdatamemberstoinitialvalues

Instancedeclaration:

book myBook;

InstancemyBook is

created

with

the

price

set

to

10.0,author settoDayang Norhayati,titlesettoLearnDataStructureandyearsetto2012

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book::book()

{ price = 10.00;

strcpy (author,Dayang Norhayati);

strcpy (title, Learn Data Structure);

year = 2012;} // end default constructor


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ConstructorwithArgument

Implementation

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book::book (char *bkTitle,double bkPrice){ strcpy (title, bkTitle);

price = bkPrice;

}

Instance declaration:book myBook(NorBahiah,25.00);

Price is set to 25.00

Authoris set to NorBahiah


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Constructor

With

Default

Argument

Implementation

2 methods oftodeclareinstanceofaclass:

book myBook; // set year to default value, 2000

book yourBook(2009); // set year to 2009

Avoidambiguityerror whenimplementingconstructor

withdefaultargument

book::book(int year);

// Constructor with default argument{ price = 10.00;

strcpy (author,NorBahiah);

strcpy (title, Learn C++);

} // end default constructor


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Destructor Destroysaninstanceofanobjectwhenthe

objectslifetime

ends

Eachclasshasonedestructor

Thecompilerwillgenerateadestructorifthe

destructoris

not

defined

Example: ~book();

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book::~book()

{ cout


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FunctionMember

Implementation

Methodto

call

the

member

function:

Frommain() ornonmemberfunction

cout title;

}

float book::checkPrice( )const

{ return price; }


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Classesas

Function

Parameters

Classobjectscanbepassedtoanotherfunctionas

parameters 3methodsofpassingclassasparametertofunction

Passbyvalue

Passbyreference

Passbyconstreference

Passbyvalue Anychangethatthefunctionmakestotheobjectisnotreflectedinthecorrespondingactualargument

inthe

calling

function.

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Passby

value

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class subject

{

private:

char subjectName[20];

char kod[8];int credit;

public:

subject (char *,char *,int k=3);

void getDetail();

friend void changeSubject(subject);};

subject:: subject (char *sub,char *kd,int kre)

{ strcpy(subjectName,sub);

strcpy(kod,kd);

credit = kre;

}

void subject:: getDetail()

{cout


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Passby

value

Continued

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// friend function implementation that receive object as

parameter

void changeSubject(subject sub); // receive object sub

{ cout > sub.subjectName;

cout > sub.kod;

cout


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Passby

reference

Anychangesthatthefunctionmakestothe

object

will

change

the

corresponding

actual

argument inthecallingfunction.

Functionprototypeforfunctionthatreceivea

referenceobject

as

parameter:

use

operator

&

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functionType functionName(className & classObject)

{

// body of the function

{


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Passby

Reference

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// pass by reference

// friend function that receive object as parameter

void changeSubject(subject &sub); // operator & is used

{ cout > sub. subjectName;

cout > sub.kod;

cout


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const Parameter Referenceparametercanbedeclaredas

const ifwe

dont

want

any

changes

being

donetothedatainthefunction.

Functionprototypeforfunctionthatreceivea

referenceobject

as

parameter.

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functionType functionName(const className & classObject)

{

// body of the function{


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const Parameter

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void changeSubject(const subject &sub);

// operator const and & is used

{ cout > sub. subjectName;

cout > sub.kod;

cout


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Classas

Return

Value

from

Function

Syntaxfordeclaringfunctionthatreturnaclassobject

Syntaxto

call

function

that

return

aclass

objectName = functionName();

where,

objectName,anobjectfromthesameclasswiththetypeofclassreturnfromthefunction. Thisobjectwillbeassignedwiththe

value

returned

from

function

functionName():functionthatreturnclass

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className functionName(parameter list)

{// function body

}


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Classas

Return

Value

from

Function

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Point findMiddlePoint(Point T1, Point T2)

{

double midX, midY;

midX = (T1.get_x() + T2.get_x()) / 2;

midY = (T1.get_y() + T2.get_y()) / 2;

Point middlePoint(midX, midY);

return middlePoint;}

Point point1(10,5), point2(-5,5);

Point point3; // use defult argumen// point3 is the point in the middle of point1 and point2

point3 = findMiddlePoint(point1,point2)

Function that return a class object, Point

Statement that call function that return a class

Returntype isaclass

CreateinstanceofPoint

Returninstance

of

Point

CallfindMiddlePoint that

returnobjectandassigntopoint3


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Arrayof

class

Agroupofobjectsfromthesameclasscanbedeclaredasarrayofaclass

Example: ArrayofclassstudentsregisteredinDataStructure

class

Arrayof

class

lecturer

teaching

at

FSKSM

ArrayofclasssubjectsofferedinSemesterI.

Everyelementinthearrayofclasshasitsown

data

member

and

function

member.

Syntaxtodeclarearrayofobjects:className arrayName[arraySize];

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class staff {

char name[20];

int age ;

float salary;

public:

void read_data() ;

{ cin >> name >> age >> salary;

void print_data()

{ cout


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Arrayof

class

2methodstocallmemberfunctionformanager array.

1. Byusingarraysubscriptinordertoaccessmanagerincertain

location

of

the

array.

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cin >> n ;

manager[n].read_data() ;

cout


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PassArray

of

Object

to

Function

class info

{

private:char medicine[15];

char disease[15];

public:

void setMed() { cin >> medicine;}

void setDisease() { cin >> disease;}char*getMedicine(){return medicine;}

char* getDisease() {return disease;}

};

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Declaration of class info that store information about the disease and therelevant medicine


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FunctioncheckMedicine(data) receivesanarrayofobject

info.

Thisfunction

requires

the

user

to

enter

the

name

of

the

diseaseandthefunctionwillsearchforthemedicinethatis

suitableforthedisease.

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PassArray

of

Object

to

Function

main()

{ info data[10];

for (int n = 0; n < 5; n++)

{ data[n].setMedicine);

data[n].setDisease();}

cout


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void checkMedicine(info x[])

{ char diseas[20];int found = 0;

cout > diseas;

for (int n = 0; n < 5; n ++)

if (strcmp(diseas, x[n].getDisease()) == 0 )

{ cout


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Pointerto

Object

Pointer storeaddressofavariable.

Pointer

can

also

store

address

of

an

object.

Examplestudent student1; // create instance of

student

student* studentPtr = &student1;

CreateapointervariablestudentPtr and

initialize

the

pointer

with

the

address

of

instance

student1

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Pointerto

Object

2methodstoaccessclassmemberthrough

pointervariable

studentPtr :

1. (*studentPtr).print()

or

2. studentPtr ->print()

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Pointerto

Object

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// pointer to object

#include

#include class student

{

private:

char name[30];

unsigned long metricNo;

public: // constructor

student(char* nama,unsigned long num)

{

no_metrik = num;

strcpy(name, nama);

}

void print()

{ cout


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Pointerto

Object

ProgramOutput

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Address of the objectAddress student1: :0x0012ff68Address student2: :0x0012ff44Pointer value

Pointer value for student1:0x0012ff68Pointer value for student2:0x0012ff44Students name: Abdullah

Students metric number: 234234


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Pointerto

Object

Operatornew canalsobeusedtoallocatememoryforapointervariable.

Operatordelete destroys

memory

for

apointer

variable.

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void main()

{

student *ptr = new student("Ahmad", 123123);

ptr -> print();

delete(ptr);

ptr = new student("Abdullah", 234234);

ptr ->print();

delete(ptr);

}


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Conclusion

and

Summary AbstractDataTypeisacollectionofdataandasetofoperationson

thedata.

Abstractionimplements

information

hiding

and

encapsulation,

wherebyothermodulescannottamperwiththedata.

InC++,abstractionisimplementedbyusingclass. Inclassdeclaration,therearedeclarationofdatamembersand

functionmembers

Functionmembersconsistsofconstructor,destructor,c++functionandconst function.

Objectcanbepassedasfunctionparameterbyvalueorbyreference.

Returntype

of

afunction

can

also

be

aclass.

AnArrayandPointercanalsobedeclaredoftypeclass.

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References

1. NorBahiah etal.Struktur data&algoritmamenggunakan C++.Penerbit UTM,2005

2. Richrd F.Gilberg andBehrouz A.Forouzan,

DataStructuresAPseudocode ApproachWithC++,Brooks/ColeThomsonLearning,2001.

12/3/2011 40

Documents

Intro to Abstract Data Types