Introduction to Introduction to ProgrammingProgramming

Lecture 39Lecture 39

Copy Copy ConstructoConstructo

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ReviewReview PointersPointers ReferencesReferences Memory AllocationMemory Allocation

PointersPointers

A pointer is a special type ofA pointer is a special type ofvariable that contain a memoryvariable that contain a memoryaddressaddress

Void PointerVoid Pointer Pointer to an IntegerPointer to an Integer Pointer to a CharacterPointer to a Character Pointer to a FloatPointer to a Float Pointer to ObjectsPointer to Objects

ReferenceReferencess

&&

consconstt

Dynamic Dynamic Memory Memory

AllocationAllocation

Native OperatorNative Operator

newnew deletedelete

int *p ;int *p ;

p = new int ;p = new int ;

delete p ;delete p ;

Dynamic Memory Allocation

int *p ;int *p ;

p = new int [ 10 ] ;p = new int [ 10 ] ;

delete [ ] p ;delete [ ] p ;

Dynamic Memory AllocationDynamic Memory Allocation

class Matrixclass Matrix{{

private :private :int * m ;int * m ;int row , col ;int row , col ;

public :public : Matrix ( int rows , int cols ) Matrix ( int rows , int cols ) {{

m = new int [ rows * cols ] ;m = new int [ rows * cols ] ; }}

} ;} ;

ExampleExample

delete [ ] delete [ ] m ;m ;

AssignmenAssignmentt

int i = 0 ;int i = 0 ;

//Initialization//Initialization

int i ;int i ;

i = 0 ; //Assignmenti = 0 ; //Assignment

Matrix m1 , m2 ;Matrix m1 , m2 ;…………

m2 = m1 ;m2 = m1 ;//Assignment Statement//Assignment Statement

Member to Member to Member Member

AssignmentAssignment

m2 = m1m2 = m1

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Pointing to the same region in memoryint *m of m1

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int *m of m2

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Pointing to the same region in memoryint *m of m1

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int *m of m2

Copy Copy ConstructoConstructo

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Call by Call by valuevalue

Deep CopyDeep CopyShallow Shallow CopyCopy

Matrix ( Matrix & ) Matrix ( Matrix & ) ; ;

Example Example class Stringclass String

{{

char * c ;char * c ;

public :public :

void void copy ( char * s ) ;copy ( char * s ) ;

String ( char * data ) ;String ( char * data ) ;

void print ( ) ;void print ( ) ;

// etc.// etc.

} ;} ;

Example Example String s1 ( “test1” ) ;String s1 ( “test1” ) ;

String s2 = s1 ;String s2 = s1 ;

s1.copy ( “this is a test” ) ; s1.copy ( “this is a test” ) ;

s2.print ( ) ;s2.print ( ) ;

int i ; int i ; i = 10 ;i = 10 ;i = i ;i = i ;

Matrix m2 ( m1 ) ;Matrix m2 ( m1 ) ;

Matrix m2 = m1 ;Matrix m2 = m1 ;

Rules Rules For dynamic memory allocationFor dynamic memory allocation

1.1. Define copy constructorDefine copy constructor

2.2. Write assignment operatorWrite assignment operator

3.3. Provide destructor Provide destructor

What have we covered What have we covered today today

Review of pointersReview of pointers– Dynamic memory allocationDynamic memory allocation

newnew DeleteDelete

For memory allocation in classes we must provideFor memory allocation in classes we must provide– ConstructorConstructor– Copy constructorCopy constructor– Assignment operatorAssignment operator– destructordestructor