Class templates can have default parameters, which means that you can specify a default data type for the template. If no argument is provided for the template, the default data type will be used. This allows for greater flexibility in using the template, as you can create a general-purpose template that can handle multiple data types while also having a default behavior. The syntax for making a parameter have a default data type is “template <typename T = defaultType>”.

#include <iostream>
using namespace std;
 
template <class T1 = int, class T2 = float, class T3 = char>
class myClass
{
public:
    T1 data1;
    T2 data2;
    T3 data3;
 
    myClass(T1 a, T2 b, T3 c)
    {
        data1 = a;
        data2 = b;
        data3 = c;
    }
    void display()
    {
        cout << "The value of a is " << data1 << endl;
        cout << "The value of b is " << data2 << endl;
        cout << "The value of c is " << data3 << endl;
    }
};
 
int main()
{
    myClass<> obj1(1, 4.3, 'C');
    obj1.display();
}

Output:

The value of a is 1
The value of b is 4.3
The value of c is C

An integer, a float, and a character are the template’s default definitions for its parameters. Now, if the programmer wants to alter the data types, they must be specifically mentioned and the object defined as in the preceding examples.

The post C++ Class Templates -Part-II first appeared on Student Projects.

Class templates with a single parameter allow you to define classes that can work with multiple data types. This can make your code more flexible and reusable. For example, you could have a template class “MyStack” that can work with both integers and strings. The syntax for declaring a single parameter class template is “template <typename T>”.

#include <iostream>
using namespace std;
 
template <class T>
class nameOfClass
{
    //body
};
 
int main()
{
    //body of main
}

The vector example clearly illustrates how templates can be utilised with just one parameter.

#include <iostream>
using namespace std;
 
template <class T>
class vector
{
    T *arr;
    int size;
};
 
int main()
{
    vector<int> v1();
    vector<float> v2();
}

B. Multiple parameters

Syntax for declaring a multiple parametrized template is,

"template <typename T, typename U, ...>"

Class templates with multiple parameters allow you to define classes that can work with more complex data types and relationships. The syntax for declaring a multiple parameter class template is “template <typename T, typename U, …>”.

#include <iostream>
using namespace std;
 
template <class T1, class T2>
class nameOfClass
{
    //body
};
 
int main()
{
    //body of main
}

Only the number of parameters we declare inside the template makes a difference. Take a look at an illustration of how to use multiple arguments in a class template.

#include <iostream>
using namespace std;
 
template <class T1, class T2>
 
class myClass
{
public:
    T1 data1;
    T2 data2;
    myClass(T1 a, T2 b)
    {
        data1 = a;
        data2 = b;
    }
    void display()
    {
        cout << this->data1 << " " << this->data2;
    }
};
 
int main()
{
    myClass<char, int> obj('C', 1);
    obj.display();
}

Output:

C 1

The post C++ Class Templates-part I first appeared on Student Projects.