Templates/Generics

- - > Template is a key word. - - > It constructs a family of related functions on class - - > Template in C++ also called as generics - - > parameterized templates   enable you to construct a family of related functions on classes. - - > Use templates when you need to write  lots of nearly identical things. There are 2 types of templates in C++ 1.Function template 2.Class template   Example of a Template in C++ - - > Template in is a parameterized type which receive data type as an argument. - - > One algorithm can be applied various data types Generic function/function template - - > Generic function perform operation on various data types - - > Generic function is function generator ,which generate number of functions based on  data type - - > Programmer does not required to overload function, using generic function compiler generate number  of functions based data types   Syntax

Template<class

type-name/place holder-name> return-type function-name(parameters) { Statements; } Type-name is a place holder name which hold data type Or Type-name is a parameter –name which hold data type as argument   Example of a Template in C++ #include<isotream.h> Template<class T> T max(T x,T y) { If (x>y) Return x; Else Return y; } Void main( ) { Int M1=max(10,20); Float M2=max(1.5,2.5) Cout<<’/n Max of two integers”<<M1; Cout<<’/n Max of two floats”<<M2; }   E.g: # include<iostream.h> (bubble sort) template <class T> void sort (T,*a,int size) { T temp; for(int i=0;i<size;i++) for (int j=0; j<size-1;j++) { if (a[j]>a[j+i} { temp=a[j]; a[j]=a[j+1]; a[j+1]=temp; } } } void main() { int a [] ={ 20,10,40,50,30}; float b[]={1.5,1.4,1.3,1.1,1.2}; clrscr(); sort(a,5); sort(b,5); int i; for(i=0;i<5;i++) cout<<”\n”<<a[i}<<”\t”<<b[i]; }  

Template having multiple parameters

# include <iostream.h> template <class t1,class t2> void print (T1x ,T2y) { cout<<”\n x=”<<x; cout<<”\n y=”<<y; } void main() { print(10,1.5f); printf(1.5f,2.5); printf(65,’A’); } void print(intx,inty) { } void print(int x, float y) { } void print(int x, char y) { }  

Class Template in C++

You use a class template(also called a generic class (for class generator) to define a pattern for class definitions Generic container classes are good examples whether you have a list of intergers or any other type the basic operations are the same(insert, delete, index,etc) you can define a class structure value with generate operations once at the system generate class definitions on the fly: syntax : template<class type-name,class type-name,…..> class  class-name { data members; member functions; }

Class template

Genaral form of defining an object of generic class class-name<type>obj; type is the name of the data that the class will be operating upon.  

Example

#include<iostream.h> template<class T> class matrix { T int a[2] [2];                // we stop 2 types means int & float only T type Templates public: void read_matrix() { for(int i=0;i<2;i++) cin>>a[i][j]; } void print_Matrix() { for(int i=0;i<2;i++) { for(int j=0;j<2;j++) cout<<a[i][j]<<”\t”; cout<<endl; }}}; void main() { Matrx<float>M2; Matrix<int>M1; cout<<”\n size is”<<sizeof(M1); M1.read_Matrix(); M2.read_Matrix(); M1.print_Matrix(); M2.Print_Matrix(); } o/p:   Size  is 8 size is 16 2 4  

Example

# include<iostream.h> template<class T> class stack { T a[10]; int top; public : stack() { top=-1; } void push(T e) { if(top)>9) cout<<”\n stack is full”; else a[++top]=e; } void pop() { if(top<0) cout<<”\n stack is empty”; ele cout<<endl<<a[top--]; } }; void main() { stack<int>stack1; stack<float>stack 2; stack1.push(10); stack1.push(20); stack1.push(30); stack1.pop(); stack1.pop(); stack2.push(1.5); stack2.push(2.5); stack2.pop(); }   Example # include<iostream.h> template<class T1,class T2> class alpha { T1 x; T2 Y; public : void need() { cout<<”\n input x,y values”; cin>>x>>y; } void print() { cout<<”\n x=”<<x; cout<<”\n y=”<<y; } }; void main() { alpha<int,float>a1; alpha<float.double>a2; clrscr(); cout<<endl<<sizeof(a1); cout<<endl<<sizeof(a2); }