2 Popular Types: C++ Template Class and C++ Template Function

Table of Contents

What is Template

Templates is one of the C++ feature that provides support for generic programming.It enable us to define generic classes and functions.

template in C++

C++ Template Concepts

Also Read: Learn 3 Types of Constructors in C++ with Best Examples

C++ Template Class

As mentioned earlier, C++ templates allow us to define generic classes. It can be Parameterized with one or more types. Container classes, which are used to manage elements of a certain type, are a typical example of this feature. By using class templates, you can implement such container classes while the element type is still open.

Syntax:

template<class T>
class classname
{
..........
..........
..........
};

Example:

#include <iostream>
using namespace std;

template <class T>
class Array {
private:
T *ptr;
int size;
public:
Array(T arr[], int s)
{
ptr = new T[s];
size = s;
for(int i = 0; i < size; i++)
ptr[i] = arr[i];
}
void display()
{
for (int i = 0; i < size; i++)
cout<<" "<<*(ptr + i);
cout<<endl;
}
};

int main() {
int arr[5] = {1, 3, 5, 7, 9};
Array<int> b(arr, 5);
b.display();
return 0;
}

C++ Template Class with Multiple Parameters

It is possible to use more than one generic data type in a class template. It can be declared as a comma separated list within the template specification.

Syntax:

template<class T1, class T2, ...>
class classname{
..........
..........
..........
};

Example:

#include<iostream>
using namespace std;
template<class T1, class T2>
class Test
{
T1 x;
T2 y;
public:
Test(T1 a, T2 b)
{
x = a;
y = b;
}
void show()
{
cout<<x<<"\t"<<"and"<<"\t"<<y<<"\n";
}
};

int main()
{
cout<<"Data type float & int passed for class template test1:"<<"\n";
Test<float, int>test1(1.23, 123);
test1.show();
cout<<"Data type int & char passed for class template test2:"<<"\n";
Test<int, char>test2(3, 'W');
test2.show();
return 0;
}

C++ Template Function

We could also define function templates that can be used to create a family of functions with different argument types. Function templates provide a functional behavior that can be called for different types. In other words, a function template represents a family of functions. The representation looks a lot like an ordinary function, except that some elements of the function are left undetermined: These elements are parameterized.

Syntax :

template<class T>
returntype functionname (arguments of type T)
{
......
......
......
}

Below program shows how a template function is defined and implemented.

#include <iostream>
#include <string>

using namespace std;

template <class T>
T Max (T &a, T &b) {
return a < b ? b:a;
}

int main () {
int x = 39;
int y = 20;
cout << "Max(x, y): " << Max(x, y) << endl;

float f1 = 13.5;
float f2 = 20.7;
cout << "Max(f1, f2): " << Max(f1, f2) << endl;

string s1 = "Hi";
string s2 = "There!!";
cout << "Max(s1, s2): " << Max(s1, s2) << endl;

return 0;
}

C++ Template Function with multiple parameters

We also can use more than one generic data type in the C++ template statement.

Syntax :

template<class T1, class T2, ...>
returntype functionname (arguments of types T1, T2, ...)
{
......
......
......
}

Below program shows how a C++ template function with multiple parameters is defined and implemented.

#include <iostream>
#include <string>

using namespace std;

template <class T1, class T2>
void display (T1 a, T2 b) {
cout<<a<<"\t"<<b<<"\n";
}

int main () {
cout<<"Call function template with int and character string type parameter"<<"\n";
display(1999, "Hi There!!");
cout<<"Call function template with float and int type parameter"<<"\n";
display(12.34, 100);

return 0;
}

Also Read: An Idiotic Guide to C++ Templates

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