Overloading Functions

You can overload a function by having multiple declarations of the same function name in the same scope. The declarations differ in the type and number of arguments in the argument list. When an overloaded function is called, the correct function is selected by comparing the types of the actual arguments with the types of the formal arguments.

Consider a function print, which displays an int. As shown in the following example, you can overload the function print to display other types, for example, double and char*. You can have three functions with the same name, each performing a similar operation on a different data type.

// This example illustrates function overloading.

#include <iostream.h>

void print(int i) { cout << " Here is int " << i << endl; }
void print(double  f) { cout << " Here is float "
                                  << f << endl; }
void print(char* c) { cout << " Here is char* " << c << endl; }
void main() {
      print(10);            // calls print(int)
      print(10.10);         // calls print(double)
      print("ten");         // calls print(char*)
}

Two function declarations are identical if all of the following are true:

• They have the same function name
• They are declared in the same scope
• They have identical argument lists

When you declare a function name more than once in the same scope, the second declaration of the function name is interpreted by the compiler as follows:

• If the return type, argument types, and number of arguments of the two declarations are identical, the second declaration is considered a declaration of the same function as the first.
• If only the return types of the two function declarations differ, the second declaration is an error.
• If either the argument types or number of arguments of the two declarations differ, the function is considered to be overloaded.

Argument Matching in Overloaded Functions
Scope in C++

Restrictions on Overloaded Functions
Member Functions