A function declaration is shown below. This example has a return type of void, indicating that
the function does not provide a result to the caller. The caller must provide two arguments for the
function to work with — an integer and a character.
void myFunction(int i, char c);
Without an actual defi nition to match this function declaration, the link stage of the compilation
process will fail because code that makes use of the function myFunction() will be calling
nonexistent code. The following defi nition prints the values of the two parameters.
void myFunction(int i, char c)
{
std::cout << “the value of i is “ << i << std::endl;
std::cout << “the value of c is “ << c << std::endl;
}
Elsewhere in the program, you can make calls to myFunction() and pass in constants or variables
for the two parameters. Some sample function calls are shown here:
myFunction(8, ‘a’);
myFunction(someInt, ‘b’);
myFunction(5, someChar);
In C++, unlike C, a function that takes no parameters just has an empty
parameter list. It is not necessary to use void to indicate that no parameters are
taken. However, you should still use void to indicate when no value is returned.
C++ functions can also return a value to the caller. The following function declaration and
defi nition is for a function that adds two numbers and returns the result.
int addNumbers(int number1, int number2);
int addNumbers(int number1, int number2)
{
int result = number1 + number2;
return result;
}
In C++11, every function has a local predefi ned variable __func__ that looks as follows:
static const char __func__[] = “function-name”;
This variable can for example be used for logging purposes:
int addNumbers(int number1, int number2)
{