Function overloading in C++ is a powerful feature that allows you to define multiple functions with the same name but with different parameter lists (types or number of parameters). This enables you to perform similar operations on different types of data or a varying number of inputs without having to come up with unique names for each function. Function overloading enhances code readability and maintainability.

Key Points of Function Overloading

1. Same Function Name: All overloaded functions must have the same name.
2. Different Parameter Lists: Each overloaded function must have a different signature, which can be achieved by varying:
   • The number of parameters
   • The types of parameters
   • The order of parameters (if they are of different types)
3. Return Type: The return type alone cannot be used to distinguish between overloaded functions. Therefore, functions must differ in their parameter list.
4. Compile-Time Polymorphism: Function overloading is a form of compile-time polymorphism, as the correct function is determined at compile time based on the arguments passed during the function call.

Example of Function Overloading

Here’s an example illustrating function overloading:

#include <iostream>

// Function to add two integers
int add(int a, int b) {
    return a + b;
}

// Function to add three integers
int add(int a, int b, int c) {
    return a + b + c;
}

// Function to add two doubles
double add(double a, double b) {
    return a + b;
}

int main() {
    std::cout << "Sum of two integers (5 + 3): " << add(5, 3) << std::endl;         // Calls int version
    std::cout << "Sum of three integers (5 + 3 + 2): " << add(5, 3, 2) << std::endl; // Calls int version with 3 parameters
    std::cout << "Sum of two doubles (5.5 + 3.3): " << add(5.5, 3.3) << std::endl;   // Calls double version
    
    return 0;
}

Output:

Sum of two integers (5 + 3): 8
Sum of three integers (5 + 3 + 2): 10
Sum of two doubles (5.5 + 3.3): 8.8

Explanation of the Example

• Overloaded Functions: The add function is defined three times with different parameter lists:
  • The first version takes two int parameters.
  • The second version takes three int parameters.
  • The third version takes two double parameters.
• Function Calls: In the main function, the correct version of add is called based on the arguments provided. The compiler resolves which function to use at compile time by matching the parameter types and counts.

Advantages of Function Overloading

1. Improved Readability: Function overloading allows the use of the same function name for similar operations, making the code easier to read and understand.
2. Code Reusability: It reduces the need to create multiple functions with different names, promoting cleaner code.
3. Flexibility: Overloaded functions can handle different data types and numbers of arguments, providing flexibility in function usage.

Limitations of Function Overloading

1. Ambiguity: If overloaded functions are not well-defined, it can lead to ambiguity during function calls, where the compiler cannot determine which version to use.
2. No Distinction by Return Type: You cannot overload functions based solely on return type. The parameters must differ.
3. Complexity in Overloading: Overloading can sometimes make the code more complex, especially if there are many overloaded versions of a function.