Motivation - Object Oriented Programming - Lecture Slides, Slides of Object Oriented Programming

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Object-Oriented Programming

(OOP)

Lecture No. 32

Motivation

• Following function prints an array of

integer elements:

void printArray(int* array, int size) { for ( int i = 0; i < size; i++ ) cout << array[ i ] << “, ”; }

...Motivation

• What if we want to print an array of

doubles?

void printArray(double* array, int size) { for ( int i = 0; i < size; i++ ) cout << array[ i ] << “, ”; }

...Motivation

• Now if we want to change the way function

prints the array. e.g. from

to

...Motivation

• What if we want to use an Array class that

wraps arrays of double?

class Array { double* pArray; int size; public: … };

...Motivation

• What if we want to use an Array class that

wraps arrays of boolean variables?

class Array { bool* pArray; int size; public: … };

Generic Programming

• Generic programming refers to programs

containing generic abstractions

• A generic program abstraction (function,

class) can be parameterized with a type

• Such abstractions can work with many

different types of data

Advantages

• Reusability
• Writability
• Maintainability

Function Templates

• A function template can be parameterized

to operate on different types of data

Declaration

template< class T > void funName( T x ); // OR template< typename T > void funName( T x ); // OR template< class T, class U, … > void funName( T x, U y, … );

…Example – Function Templates

int main() { int iArray[5] = { 1, 2, 3, 4, 5 }; void printArray( iArray, 5 ); // Instantiated for int[] char cArray[3] = { ‘a’, ‘b’, ‘c’ }; void printArray( cArray, 3 ); // Instantiated for char[] return 0; }

Explicit Type Parameterization

• A function template may not have any

parameter

template T getInput() { T x; cin >> x; return x; }

…Explicit Type

Parameterization

int main() { int x; x = getInput< int >(); double y; y = getInput< double >(); }

User-defined Specializations

• A template may not handle all the types

successfully

• Explicit specializations need to be

provided for specific type(s)