CPP Templates

CPP templates acts as a support for generic programming technique, where parameters in algorithms are of generic types and thus can work for a variety of data types. This feature in CPP is used to define the generic classes and generic functions.

Types of CPP Templates:

Function Templates:

In function templates, templates for a function is defined.

Syntax:

template < class Ttype> ret_type func_name(parameter_list)

{

// code to be executed

}

Ttype:

This parameter is used to represent a placeholder name, to be replaced by the compiler, for a data type, within the function definition.

class:

This keyword is used before Ttype to specify a generic type in a template declaration.

Syntax: Function Templates with Multiple Parameters:

template <class T1, class T2,…..>

return_type function_name (arguments of type T1, T2….)

{

// code to be executed

}

Important points:

Function template is used by generic functions to define a set of operations that can be applied to the various types of data.
The generic functions can be overloaded by overloading the template functions (can differ in the parameter list).
For all the versions of a function, a generic function executes the same operation for the same data type.

Example:

#include <iostream.h>  
using namespace std;  
template<class A> A mul(A &x,A &y,A &z)  
{  
A product = x*y*z;  
return product;  
}  
int main()  
{  
float n1 = 50;  
float n2 = 40;  
float n3 = 30;
cout<<"Product of " << n1 << ", " << n2 << " and " << n3 <<" is : "<< mul(n1,n2,n3);  
return 0;  
}

Output

Product of 50, 40 and 30 is : 60000

Class Template:

In class templates, templates for a class is defined.

Syntax:

template <class Ttype>

class class_name

{

// code to be executed

}

Ttype:

This parameter is used to represent a placeholder name, to be replaced by the compiler, for a data type, within the class definition.

Syntax: Creating an instance of a class

class_name <type> ob;

type:

This parameter is used to specify the type of the data that the class is operating on.

ob:

This parameter is used to specify the name of the object.

Syntax: Class Templates with Multiple Parameters:

template<class T1, class T2, ……>

class class_name

{

// code to be executed

}

Non Type Template Arguments

The non-type arguments such as strings, function names, constant expression and built-in types can also be used in addition to the type T argument.

Example:

#include <iostream.h>  
using namespace std;  
template<class X>  
class A   
{  
public:  
X n1 = 50;  
X n2 = 20;  
X n3 = 30;
void mul()  
{  
std::cout<<"Product of " << n1 << ", " << n2 << " and " << n3 <<" is : "<< n1*n2*n3<<std::endl;  
}  
};  
 
int main()  
{  
A<int> m;  
m.mul();  
return 0;  
}

Output

Product of 50, 20 and 30 is : 30000

CPP examples programs

Syntax: