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Template and

exception

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Template

Template make it possible to use one function or class to handle different

data types syntax:

template <class T>

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HOW TEMPLATE CAN USE

Template concept can be use in two different conceptsi. Function templateii. Class template

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FUNCTION TEMPLATE

The body of the function template is written in the same way in each case as function is written but the difference is that they can handle arguments and return value of different types.

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EXAMPLE Template function:

template <class T> void get(T a) { cout <<" value : "<<a; cin.get(); } void main() { int a=5;float b=4.3;get(a);get(b);

}

Simple function:

void get(int a) { cout <<" value : "<<a; cin.get(); getch(); } void main() { int a=5;float b=4.3;get(a);get(b);

}

Function Template

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OUTPUT Function Template: Simple Function

Continued…

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TEMPLATE RETURN TYPE

template <class T> T square(T value){return value*value;}int main(){int a=5;float b=7.5;long c=50000900000;double d=784848.33;cout<<"square of int variable is : "<<square(a)<<endl;cout<<"square of long variable is : "<<square(b)<<endl;cout<<"square of long variable is : "<<square (c)<<endl;cout<<"square of double variable is : "<<square(d)<<endl;cin.get();getch();}

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Function template with multiple arguments

template<class t > void get( t x, t y , int c) { int sum; sum=x+y+c; cout<<sum; cin.get(); getch(); }

void main()

{ int a=6; int b=9; int c=8; get(a,b,c); }

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EXAMPLE template<class t, class v > void get(t x, v y ,int c) { v sum; sum=x+y+c; cout<<sum; cin.get(); getch(); } void main() { int a=6; float b=9.9; int c=8; get(a,b,c); }

Output:

Function Template

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CLASS TEMPLATE

Class template definition does not changeClass template work for variable of all types instead of single basic type

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Example 1template <class t>class Basket{t first;t second;public:Basket (t a, t b){first = a;second = b;}t Bat(){return (first > second?

first:second);}}; //class end

void main(){Basket <int> bo(6,8);cout<<bo.Bat()<<endl;Basket <float> b1(1.1,3.3);cout<<b1.Bat()<<endl;system ("pause");}

Output:

83.3

Class Template

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If we write Basket <int> b(6.99,8.88);Instead of Basket <int> b(6,8);Output will be in integers i.e 8

Continued…

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Example 2template <class t>class Basket{t first;t second;public:Basket (t a, t b){first = a;second = b;}t Big();}; //class end

template <class t>t Basket <t>::Big(){return (first > second?first:second);}

void main(){Basket <int> b(6,8);cout<<b.Big()<<endl;Basket <float>

b1(4.1,1.1);cout<<b1.Big()<<end

l;system ("pause");}

Output:

84.1

Class Template

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template <class t>t Basket <t>::Big(){

return (first > second?first:second);

}

The name Basket<t> is used to identify the class of which Big() is a member function . In a normal non-template member function the name Basket alone would suffice.Void Basket :: Big(){

return (first > second?first:second);

}

Continued…

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workingint Basket<int>::Big(){return (first > second?first:second);}float Basket<float>::Big(){return (first > second?first:second);}

Continued…

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LINKED LIST CLASS USING TEMPLATES

template<class TYPE> struct link { TYPE data; link* next; }; template<class TYPE> class linklist { private: link<TYPE>* first; public:linklist() { first = NULL; }void additem(TYPE d); void display(); };

template<class TYPE> void linklist<TYPE>::additem(TYPE d) { link<TYPE>* newlink = new link<TYPE>; newlink->data = d; newlink->next = first; first = newlink; } template<class TYPE> void linklist<TYPE>::display() { link<TYPE>* current = first; while( current != NULL )

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{

cout << endl << current->data; current = current->next; } }

int main() { linklist<double> ld; ld.additem(151.5); ld.additem(262.6); ld.additem(373.7); ld.display();

linklist<char> lch;

lch.additem('a'); lch.additem('b'); lch.additem('c'); lch.display(); cout << endl; system("pause");

}OUTPUT

373.7262.6151.5

cba

Continued…

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EXCEPTIONAn exception is a condition that occurs at execution time and make normal continuation of program impossible.

When an exception occurs, the program must either terminate or jump to special code for handling the exception.

Divide by zero errors. Accessing the element of an array

beyond its range Invalid input Hard disk crash Opening a non existent file

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EXCEPTION HANDLING

The way of handling anomalous situations in a program-run is known as exception handling.

Its advantage are:

Exception handling separate error-handling code from normal code.

It clarifies the code and enhances readability Catch error s before it occurs. It makes for clear, robust and fault -tolerant program

s.

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EXCEPTION HANDLING IN C++

Tries a block of code that may contain exception

Throws an exception when one is detected

Catches the exception and handles it Thus there are three concepts

i. The try block ii.The throwing of the exception iii.The catch block

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TRY BLOCK A block which includes the code that may

generate the error(an exception) try { …. } Can be followed by one or more catch blocks

which handles the exception Control of the program passes from the

statements in the try block ,to the appropriate catch block.

Functions called try block, directly or indirectly, could test for the presence of the error

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THE THROW POINT Used to indicate that an exception has

occurred Will be caught by closest exception

handler Syntax:-

if ( // error) { Throw error(); }

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THE CATCH BLOCK Contain the exception handler. These know what to do with the

exception-typically print out that a type of error has occurred.

Catch blocks are typically located right after the try block that could throw the exception

Syntax:- catch() { ….. }

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EXCEPTION MECHANISM

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Exampleconst int DivideByZero = 10;double divide(double x,

double y){ if(y==0) { throw DivideByZero; } return x/y;} int main(){try{ divide(10, 0);}

catch(int i){ if(i==DivideByZero) { cout<<"Divide by zero

error"; }cin.get();}}

Output:-Divide by zero error

Exceptions

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EXCEPTION SYNTAX Class Aclass {

Public: Class Anerror {

}; Void func() { if(/*error condition*/)

Throw Anerror(); } };

Int main(){Try{Aclass object1;Object1.fun();

}Catch (Aclass ::Anerror)

//may cause error{//tell user about error}Return 0;}

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MULTIPLE CATCH STATEMENT

try{

//try block}catch(type1 arg){

//catch block1}catch(type2 arg){

//catch block2}

…….…….catch(typeN arg){

//catch blockN}

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Exampleconst int Max=3;class stack{private:int st[Max],top;public:class full{};Class empty{};stack(){top=-1;}

void push(int var){if(top>=Max-1)throw full();st[++top]=var;}Int pop(){if(top<0)Throw empty();Return st [top--];}};

Multiple Exceptions

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int main(){stack s1; try{s1.push(11); s1.push(22);s1.push(33); s1.push(44);S1.pop(); s1.pop();S1.pop(); s1.pop(); }catch(stack::full){cout<<"exception :stack

full"<<endl;}

Catch(stack::empty){Cout<<“exception: stack

empty”<<endl;}cin.get(); }

Continued…

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Exceptions with the Distance Class

class Distance{private:int feet;float inches;public:class InchesEx { };Distance(){ feet = 0; inches = 0.0; }Distance(int ft, float in) {if(in >= 12.0) throw InchesEx(); feet = ft;inches = in;}

void getdist(){cout << "\nEnter feet: "; cin

>> feet;cout << "Enter inches: "; cin

>> inches;if(inches >= 12.0) throw InchesEx();}void showdist(){ cout << feet << "\’-" <<

inches; }};

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int main(){try{Distance dist1(17, 3.5); Distance dist2; dist2.getdist();cout << "\ndist1 = "; dist1.showdist();cout << "\ndist2 = "; dist2.showdist();}catch(Distance::InchesEx){cout << "\nInitialization error: ";cout<< "inches value is too large.";}cout << endl;return 0;}

Continued…

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Exceptions with Arguments

class Distance {private:int feet;float inches;public:class InchesEx {public:string origin; float iValue; InchesEx(string or, float in){origin = or; iValue = in; }};

Distance() { feet = 0; inches = 0.0; }Distance(int ft, float in){if(in >= 12.0)throw InchesEx("2-arg

constructor", in);feet = ft;inches = in;}void getdist(){cout << "\nEnter feet: "; cin

>> feet;cout << "Enter inches: "; cin

>> inches;

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if(inches >= 12.0)throw InchesEx("getdist()

function", inches);}void showdist() { cout << feet << "\’-" <<

inches; }};void main(){try{Distance dist1(17, 3.5); Distance dist2;

dist2.getdist();cout << "\ndist1 = ";dist1.showdist();cout << "\ndist2 = ";dist2.showdist();}catch(Distance::InchesEx ix){cout << "\nInitialization

error in " << ix.origin<< ".\n Inches value of " <<

ix.iValue<< " is too large.";}

Continued…

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SPECIFYING DATA IN EXCEPTION

CLASSclass InchesEx {public:string origin; float iValue; InchesEx(string or, float in){origin = or; iValue = in; }};

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Bad_alloc Extracting data from the exception object

int main(){const unsigned long SIZE = 10000; char* ptr; try{ptr = new char[SIZE]; }catch(bad_alloc){cout << “\nbad_alloc exception: can’t allocate memory.\n”;return(1);}delete[] ptr; //deallocate memorycout << “\nMemory use is successful.\n”;return 0;}