Overloading function templates in C++

Template:

• A template is a tool that reduces the efforts in writing the same code as templates can be used at those places.
• A template function can be overloaded either by a non-template function or using an ordinary function template.

Function Overloading: In function overloading, the function may have the same definition, but with different arguments. Below is the C++ program to illustrate function overloading:

C++

// C++ program to demonstrate the
// function overloading
#include <bits/stdc++.h>
using namespace std;

// Function to calculate square
void square(int a)
{
    cout << "Square of " << a
         << " is " << a * a
         << endl;
}

// Function to calculate square
void square(double a)
{
    cout << "Square of " << a
         << " is " << a * a
         << endl;
}

// Driver Code
int main()
{
    // Function Call for side as
    // 9 i.e., integer
    square(9);

    // Function Call for side as
    // 2.25 i.e., double
    square(2.25);
    return 0;
}

Output:

Square of 9 is 81
Square of 2.25 is 5.0625

Explanation:

• In the above code, the square is overloaded with different parameters.
• The function square can be overloaded with other arguments too, which requires the same name and different arguments every time.
• To reduce these efforts, C++ has introduced a generic type called function template.
  

Function Template: The function template has the same syntax as a regular function, but it starts with a keyword template followed by template parameters enclosed inside angular brackets <>.

template <class T>

T functionName(T arguments)
{
     // Function definition
     ……….  ……   ….. …….
}
where, T is template argument accepting different arguments and class is a keyword. 

Template Function Overloading:

• The name of the function templates are the same but called with different arguments is known as function template overloading.
• If the function template is with the ordinary template, the name of the function remains the same but the number of parameters differs.
• When a function template is overloaded with a non-template function, the function name remains the same but the function’s arguments are unlike.

Below is the program to illustrate overloading of template function using an explicit function:

C++

// C++ program to illustrate overloading
// of template function using an
// explicit function
#include <bits/stdc++.h>
using namespace std;

// Template declaration
template <class T>

// Template overloading of function
void display(T t1)
{
    cout << "Displaying Template: "
         << t1 << "\n";
}

// Template overloading of function
void display(int t1)
{
    cout << "Explicitly display: "
         << t1 << "\n";
}

// Driver Code
int main()
{
    // Function Call with a
    // different arguments
    display(200);
    display(12.40);
    display('G');

    return 0;
}

Output:

Explicitly display: 200
Displaying Template: 12.4
Displaying Template: G